I don't see what you're getting at here, outside of armor proficiency feats. Either your two main stats include Dex or Int (and thus you're ok with light armor, either way), or it doesn't (in which case you'll need heavy armor. The great starting stats just push it back from Heroic to Mid-Paragon)
Armor proficiency, hafted defense, TWD, shield feats, specialization, etc are normally not all possible to stack up. Again just looking at fighters you get the option to crank on a specific weapon (lets say hammers), pick up several of these types of feats, and STILL have a significantly higher strength and wisdom, which in turn can open up several more feats.
You have a reference? It certainly looked to me that the feat sections in later books have much fewer stat requirements. (Now, PHB1 has a lot of really important feats, so stat requirements are still important for characters)
I simply went through and added up numbers of feats in different books that had prereqs and binned them a bit. My recollection is that PHB1 indeed has the most prereqs (by a good distance at epic) but after that all the other books are close to the same. There was no downward trend and all of them have a substantial number of feats that have prereqs. I didn't include PHB3 at the time as it wasn't out. Just eyeballing it looks like that book does have very few, but it also has very few general feats of any kind (5 epic tier feats that are not race or class specific, total).
The point is even discounting PHB1 feats there are a lot of feats and often many of the best ones that do have prereqs. The other aspect of that is that the game tends to channel people's focus into specific areas using prereqs. Even if you CAN take feat A that relates to build X without a decent stat you can't take feat B that really makes that choice worthwhile so its largely moot.
Such as? I know polearms are rather MAD, but it was possible to pull off on a standard point buy. Broom builds are just a bit easier now. Don't see that as a huge change (and really, don't see Broom builds as a serious issue anyway)
Except normally if you are going to run a build like that you are not also going to be affording armor specialization, crit fishing feats, etc AT THE SAME TIME. No one of those things is by itself a serious issue. When you can stack together a bunch of stuff that normally simply cannot be combined it WILL give someone with a good knowledge of the system a way to boost themselves a lot in epic. Like I said a few posts ago, its not going to break the system, there are limits to what you can accomplish overall (sans a few total cheese builds that really have nothing to do with ability score anyway, there could be a couple more of those opened up but I don't know for sure).
One of the main problems with this kind of discussion is there just haven't been people spending time exploring what can and can't be done with non-legal array builds. You can find 1000's of pages of information on optimizing WITHIN the legal arrays, but nobody bothers to go outside that. For one thing it just isn't that challenging, but mainly most players that are into that kind of thing want legal builds. Sitting down with CB and playing around would be informative though. I think you may be surprised at how much mileage you can get out of even just a couple extra points in a couple of key stats.