Scurvy-Platypus, your post was very long and detailed, I will refrain from quoting it and answering in detail, but here are some points:
Heh. I do tend to go on at times.

Since I've the luxury of time at the moment, I'll go ahead and address your points...
- Rule Zero is expected to be used in every RPG. IMHO, it is a sign of good game design, if it is only needed sparingly.
Rule Zero is a surprisingly contentious thing. How a person deals with it is... *shrug*... well, personal. I won't expound really on this other than noting your point.
- What is the purpose for different point cost, if not balancing? What is a reason for a non-absolute Point-Buy system?
I think we got a crossed wire somewhere. Yes, altering point cost is a function of balancing, especially given that the book specifically addressing modifying it if necessary to better suit the particular game being played. I'm not quite sure where you're going with the point, so I don't know how to respond. I know I'm not saying that BESMd20 is _unconcerned_ with balance; it's just looking at "balance" from a slightly different perspective.
As for the reason for a non-absolute Point-Buy system?
Well, one thing that immediately occurs to me is the issue of "Attribute [x] is overpowered because [fill in the blank]!" You see stuff like this all the time in regular d20 conversations with someone declaring how this or that character class has an overpowered ability because they can abuse it and produce some sort of wildly off the chart result from the games base assumptions. This is followed by other posters showing up and going "Hmmm. Not disagreeing with your point, but... it's never been a problem in my game."
People have a tendency to treat rule texts as "fixed" (unalterable) unless there's an explicit out given; Rule Zero is usually the recourse of the GM at that point, which is one reason why it's included. But as mentioned it's also contentious. A relative point-based system allows for the GM to easily say, "The game has been balanced with [this] expectation in mind. However, for [whatever reason] I'm going to change the cost of [offending attribute] because that is going to lead to a game I like running better."
Another reason is an explicit "dial" for tuning the game. By having a relative system, people are more likely to play around with things in the game to produce something closer than what they might have. For example, maybe they want to promote a more aggressive game, they'll lower the cost of attacks, or alter the cost of defences. Or certain types of things (like magic) are made more expensive, to reflect running a "lower magic" setting.
The issue of something like a "lower magic" setting is critical. This forum is lousy with people complaining about the power assumptions of D&D and wanting to run an S&S-style game or "low magic" or "gritty"... it's a popular sub-type of game that's been a part of rpgs for more than the 2 decades and some odd years I've been involved in rpgs. Talk about it in D&D (3.x or 4E) and you'll have a whole chunk of people to talk about the problems systemically with doing that and how to try and account for it; that's because the game carries a built-in assumption and no dial for dealing with it. Relative point-buy is one way of doing so; it might be a poor way in some people's opinion, but it is an option offered that many other games don't explicitly give.
The relative point-buy suits designer bias better in this case.
Note: the following opinion is not intended to start an argument regarding playstyles. It's intended to illustrate 2 very real approaches to characters, without passing a judgment as to which is better.
Opinion: People have 1 of two methods for designing characters. They have an explicit idea ["I wanna play a character like Rogue from the X-Men!"] or they decide on a particular theme/set of abilities and then "backfill" a character in terms of history etc. A sort of "top up" vs "top down" design, much like how GMs approach worldbuilding.
The designer of Tri-Stat and BESMd20 has a very "relationship-based" sort of approach to rpgs. GMs are explicitly supposed to be working with players to produce a type of game, there's a greater shared responsibility, instead of it resting solely with the GM etc. The rules are laid out with an expectation that players will _not_ try and abuse them, because it's understood that _any_ rule system can be abused in the first place. In cases where abuse is possible to occur, then the expectation is the GM will step forward and draw a line.
d20 on the other hand comes from a position where the rules are legislating both player and GM behavior. This isn't necessarily a bad thing or an unneeded thing, it's simply a fundamentally different expectation.
- The failed class deconstruction is unconnected to CR.
Actually, this complaint isn't limited to just BESMd20. As far as I know, no system designed using the 3.x rules is actually explicitly connected to CR. It's a fundamental weakness of most 3.x systems to begin with: the character system is not really related to the same system used for opposition. That's what I was trying to get at earlier.
3.x has the conceit that monsters can be given class levels. Ooooo, everyone's excited. Even now, a decade later it's still more common for critters to have class levels than it is for templates to be used.
The problem of course is that characters and monsters _aren't_ equivalent, regardless of crap like ELC and people's jumping through hoops to justify it. Monsters are theoretically built with an expectation that 1 creature is capable of using up 20% of a party's resources, said party being 5 person. The problem comes from the design assumption that people are going to try and abuse the rules, which explicitly limit character resources; monster's abilities are generally resource-free and therefore within the designs of 3.x and the sensibilities of most people playing/running the game those abilities are stronger in the hands of players.
M&M gets around this problem I believe in a few ways.
1. It's not focused on fighting "the other" in the same way that D&D is. D&D is about killing things and taking their stuff. Most things are "monsters" even if they're intelligent humanoids, so it's ok to engage in genocide. M&M on the other hand is more about supers fighting, which has a number of conceits, such as not killing villains, most of the opponents are "humans" (even if they have bumpy foreheads) instead of mindless beasts, and of course, they're fighting people of equal or even slightly greater capability.
2. The opposition is basically built using the same system as the PCs. This introduces a fundamental degree of parity that's lacking in other 3.x system.
M&M doesn't tie into the CR system, it completely ignores it. That works for what it wants to do, but it does have the consequence of completely ignoring decent chunks of 3.x material that might otherwise be compatible.
3. A fundamental design aspect of 3.x is limited resources. M&M uncaps this significantly, which is also in keeping with supers style. Characters aren't focused on that zero-to-hero crawl, which is an obsession with most people that play D&D; characters starting incompetent and then gaining skill.
M&M characters are Han Solo, starting off bad-ass and mostly staying that way with minor change.
D&D characters are Luke Skywalker, starting off pathetic and eventually reaching a point of ... well, whatever.
This is both a design of the games, as well as a focus of playstyles by people that _play_ those games. If you wanted, you _could_ start a D&D game at 10th level and never level up. Just acquire gear or whatever. Hell, it's common enough in plenty of books that gamers like to read; characters in those books not really changing, just going off and having adventures of one sort or another.
But I've never heard of people actually running a D&D game like that. Even E6 which is a large step in that direction is usually advocated by people intent on limiting character power (trying for a "gritty" or "low magic" game) and still features a whole series of capstone feats or somesuch intended to still increase the power but in their own idiosyncratic way.
All of which is why I'm personally somewhat leery of things like Complete Control, Buy the Numbers, Eclipse: Persona Codex, etc. Or an attempt to "rebalance" BESMd20. They're not explicitly (or at least not obviously to me) looking at the fundamental system that characters are engaging in (creatures built using the CR guesstimate of WotC and others) and then balancing it in relation to an explicit version of that system. Instead they're messing around with balance in relation to other classes/abilities and combat which may or may not be "accurate" due to playstyle and optimisation skills.
Which, like I said before, is one reason why I'm such a fan of Upper_Krust's CR system. I'm not sure how exactly he derived the numbers, but... I'm not super-concerned about the exact nature of the derivation either. What's important is that he looked at CRs and the creatures using CR, and developed an explicit system that was intended to reflect the design assumptions of those creatures. In some cases, it means some creatures (like dragons) have the "wrong" CR, because the capabilities of those creatures is in fact in excess of the rest of the CR system.
Using UK's CR system, it's possible to look at a class and what they get and at least approximate what that class' capabilities are in comparison to not only what they're going to frequently face (monsters relying at least partially on the CR system) but also other classes.
The problem of course is that it's just plain hard work and the reward for doing it is pretty minimal as far as most people are concerned. Especially since you'll eventually run into the deliberate imbalances that exist and have to make a decision regarding how to deal with that.
- Assumptions from Tri-Stat: Tri-Stat works actually better and uses PMVs to modify Attributes. This option isn't part of BESM d20.
Yes and no.
BESMd20 is built from SASd20. There are some differences between the two, but they're substantially the same. One thing that didn't get moved over into BESMd20 is PMVs. They do however exist explicitly within the OGC of SASd20.
Now, wanna know something interesting?
My 1st Ed 2nd Printing copy of M&M's OGL declaration only lists the SRD and of course itself in the copyright section; that's section 15 where you're supposed to list the copyrights of products used in your game, for folks that aren't OGL nerds.
My copy of M&M Pocket Player's Guide (which is 2nd Ed rules) lists SASd20 in its section 15.
So, strictly speaking, you're right PMVs aren't in BESMd20 by default. They do however exist in SASd20 and while there are some differences between the two, my casual comparison between the Stingy Gamer's Edition of both of them hasn't shown that there'd be a substantive issue with pulling over the "missing" bits from SASd20 to BESMd20.
And those rules are OGC baby.
- I would really appreciate, if you can point me at the power ceiling rules.
So I went looking and as a part of default BESMd20, I don't see ceiling rules. I don't see them as part of SASd20 either. The limitation that they appear to have is that CP are being handed out explicitly and in limited quantities, unlike M&M which just gives you a big ol' chunk of 'em and tells you to go wild.
SASd20/BESMd20 are appear to be relying on the nature of the game being a class/level based one to keep things capped.
So, where'd I come across it?
There's a BESMd20-derived fantasy game called "Everstone"; I'm a huge fan of it and I've gone on about it before. Anyway, the way the classes are constructed there's a chunk of 5 CP given every level. Page 44 of the book says, "Remember you cannot have any Racial or Class Attribute higher than 3 because there is a limit of purchasing 1 rank per attribute per level." The character starting level is 3, so that's an internally consistent reminder.
It's a logical attempt to try and limit things and introduces an effective ceiling like you're talking about, but I don't seem to be able to find an actual BESMd20 source for that rule. It's not entirely surprising since the game does deviate from base BESMd20 in a number of respects.
So yeah, looks like BESMd20 has dropped the ball in terms of providing an explicit ceiling like M&M; they're instead relying on the class structure to try and keep things capped.
- I like balance, so I will always argue for it
Fair enough. It's just that "balance" isn't an immutable term; it's at least partially in the eye of the beholder.
- The BESM d20 rules may be character centric, but there are also the greatest 'mistakes' (Attribute costs, etc).
Yup. I suspect that some of it is "copy/paste" syndrome, which is something that's popped up in some games that are 3.x based. BESMd20 and SASd20 have been built in a large part from the Tri-Stat rules and descriptions which were then ... translated?... across to the d20 system. In the process, I think some things didn't get altered like they should have been and lack of d20 system mastery resulted in what we see.
And now some points regarding BESM d20 vs M&M:
- In M&M 1, each 'effect' costs 1 PP. Powers add their 'effects' and add 1 PP surcharge. This is much more systematic than BESM d20.
Fair enough. I've never played M&M so I can't really comment on what the design philosophy was in the first place. Conversations about "converting" a d20 character into M&M have _always_ resulted in people basically saying "you really can't, you'll need to rebuild the character" so... I dunno. BESMd20 and SASd20 were explicitly trying to tap into (and be compatible with) the d20 system.
M&M on the other hand was looking to take the d20 system and do something _different_ with it. There's other super games before M&M, they just don't register in most people's memory.
So SASd20/BESMd20 and M&M sort of arrived in a similar place, but from different origins and with different goals. In retrospect, M&M's has the greater degree of system coherency, but I think I can understand how/why BESMd20 wound up the way it did.
- Neither BESM d20 nor M&M are compatible with the 3.5 or modern SRD. But IMHO, the more systematic structure of M&M makes it actually easier to backward engineering it to make it compatible.
I'd disagree. As I mentioned above, BESMd20 was explicitly looking to be compatible, while M&M was explicitly looking to move away from it. One of M&M 1st Ed criticisms frequently was that it was "too much like D&D". There was a distinct anti-D&D crowd that adopted M&M and that combined with flaws in the 3.x design made it easy for M&M to evolve further away from the 3.x base it started with.
BESMd20 also explicitly has gone out of its way to try and provide information to allow people to reverse-engineer other d20 things into the BESMd20 system; especially when you look at the other books like BESMd20 mecha. Monstrous Manual, and Advanced Magic. Now, there's flaws within the BESMd20 products stemming from some of the design assumptions (as we've already covered and both agree on I think), but for all their flaws those tools are still there.
M&M doesn't have a conversion of SRD critters, nor does it address the issue of 3.x spells really. Sure, there's fan stuff but in terms of "official" whatever... you're told "build it yourself" and given some vague guidelines. Now, the world of 3.x games isn't just critters and magic, but it's taken a long time for M&M to even address vaguely what BESMd20 addressed quite early and far more substantively.
And of course that also means that M&M is able to look at the mistakes made by others (like GoO) and theoretically avoid making them. One of the dangers in being first is that if you screw up, you become a "baseline" with people pointing to your screwups and how someone later avoided it.
- The names/words 'Hero Points' and 'Power Points' are IP. Hero Points is a bit difficult, as Paizo used the same name for points with a similar effect (they are all derived from the UA 'Action Points') and made them OGC...
And just replace the term 'Power Points' with 'Building/Character Points' in the text and the rules chapters of M&M become fully OGC.
Yup.
Personally, I like to go as close to the source as possible; I'd rather avoid Pathfinder if I can just go to an earlier source and use from that instead. So I'd just go with Action Points from UA and call it good. But that's personal preference and in this particular case it's partially born of the fact that I actively dislike the implementation of almost all the Action Point systems I've seen used for d20; yes, that includes Trailblazer.
I know that philosophically we're sitting on rather different ends of the spectrum Walking Dad. I don't expect to "change your mind" or "prove you wrong" or anything like that. You've your preferences and opinions and I've got mine. My main goal in responding as I have is to try and show a counter-point to a common enough perspective, given that BESMd20 is almost always and forever in the shadow of M&M.
At the end of that day... *shrug* ... like I said, 1st ed M&M and BESMd20 (especially SASd20) have a fair amount of similarities. From a design perspective, M&M is more inline with a number of assumptions and expectations of the general d20 audience, regardless of whether that d20 audience likes or hates D&D specifically. There really isn't a "good" reason for choosing BESMd20 over M&M when looking explicitly at system concerns. Skill-based combat is the really big difference between them.
From a publishing perspective, you probably would be better off just sucking it up and trying to get an M&M license, as you'll at least have an audience; M&M is active and liked, whereas BESMd20 is "unsupported" and actively disliked by many of those folks that know about it, which is rather small these days. Walking Dad's posts really kinda illustrate it; most people aren't interested in BESMd20 and using it is going to be a stigma unless you're very aware of what you're trying to do and how you get there.
I'm personally using BESMd20 for my projects, for a number of reasons. Given that what I want to do and achieve is "niche" in the first place, I'm not going to be trying to make money off of them in the second place, and I'm introducing a fair number of core changes in the third, I'm not particularly concerned about the parentage of my stuff.