I'm coming at this from a more practical, in-play standpoint.
No, no,
I'm coming at this from a more practical, in-play standpoint.
You are clearly coming to this from a theoretical 'this is how you should design things' tag line that someone wrote in the subheading of an essay with a title like 'Six elements of good design'. I can hear your formalism rolling around in the background quite clearly, but my preference comes from practical, play-tested, organic, evolutionary play.
One of the reasons I have a hard time getting excited any more about point buy systems is that they fail hard on this test. Novice players create interesting well-rounded characters. But players eventually evolve to create characters that efficiently use the space on the character sheet and have only character defining powers. This is not a good thing. You end up with wacky balance. Everyone has a hammer, and they have to use the hammer for solving every problem that they have. Either the hammer just smashes the problem because well, with every single point invested in being good at that one thing, they are really really good at it, or else the hammer doesn't work and they are completely helpless. Every situation becomes basically binary and the GM is forced to metagame as a consequence. Having nothing on your character sheet that isn't immediately useful is a disaster in play for everyone at the table.
There's a big gulf between "use all the time" (like an attack roll, forex) and "use at least 1/session," and I don't count "making you have largely pointless abilities" as a value-added element of the class system. It's the old tiger repellant scheme: if you don't ever actually have to use it, there's no real value in it.
No no no. It's hugely valuable. It means that I as the GM never have to think, "Can I use tigers? Because I'm not sure anyone is going to have a relevant ability and if I use tigers, it could mean a TPK" or conversely, "What's the point of using tigers? Tigers aren't even a challenge since player X has fully invested in Super Tiger Repellant". It also means that players occasionally have to go, "Crap, the hammer doesn't work. I wonder if this screwdriver might be effective." Or sometimes, "Hmmm.. I have tiger repellant. Maybe that will be useful."
I specifically had in mind effects like sudden changes in weather or venomous patches of unknown plants or hillsides in rain that would give way with a bit of pressure.
In the case of say an avalanche or a flash flood or similar hazards, I would tend to have the Trap Sense apply to any relevant AC or Reflex saves to avoid it (if any), because well, it's functionally equivalent to a planned trap that sends some hazard sliding and bouncing the way of the rogue. Gravity is gravity. I might sometimes use a different skill to recognize the hazard than 'search', but I'm probably literally recording the physical hazard as a trap when I make my notes. Just because someone didn't do it on purpose, doesn't mean it's not a trap.
I'm undecided/unconvinced on the value of replacing 'rogue sense' with a generic 'danger sense'. I toyed with embracing the option that I gave Ahnehnois of 'pick two' for a while just because I like the diversity and flavor of his list, but I think at this point I've tentatively abandoned that due to the complexity of balance and the fact that most do something redundant with some other character building resource.
As I said, my current version of the rogue has a Rogue Sense which is equivalent to having Ahnehnois's 'Trap Sense' and 'Spell Sense' simultaneously. In play, I find this plenty broad enough to be useful while avoiding trampling on anyone else's space and also avoiding problems I see in wording a generic 'danger sense' well and simply so as to avoid arguments as to when it applied. The rogue has used 'rogue sense' in both manners multiple times at this point, and the prior rogue using my current version of the rules also used both on occasion. Play testing is convincing.
I also largely think that making the rogue's 'trap sense' as generic as a 'danger sense' risks a double mechanical dip of trope establishment (doing two slightly different things to establish the same skill), given that the rogue already has advantages like Uncanny Dodge, good Reflex saves, and so forth that apply in most or all cases that 'danger sense' would apply. More broadly, Ahnehnois's selectable +1 bonuses do very little that couldn't be accomplished by replacing the whole 'sense' concept with 2-3 bonus feats from a generic list of +X feats (Iron Will, Courage, Endurance, Skill Focus, etc.). So I'd need both a compelling reason to give the rogue the equivalent of a few feats, and a compelling reason to do this instead of something like 'trap sense'.
The Rogue Talents I like better, but have much the same issue. Basically you are just adding 2 rogue bonus feats to the progression, and unlike Ahnehnois I think one is going to amount to a feat tax in any campaign where you aren't certain ahead of time that traps won't come up because someone in the party needs to be able to deal with traps. Unlike the other things on the list, Trap Finding is an absolute. If you don't have it, every trap with a DC above 20 is undetectable. To be able to deal with a whole class of hazards for the investment of 1 feat is a no brainer. Even if you don't plan on disarming mechanical traps, just finding them and locating them has huge value.
Again, unless the rogue is poorly balanced and not a baseline, giving the rogue a few feats seems like 'Power creep is the solution to everything' thinking. If you want to be Resourceful and Daring, why can't you take Endurance and Courage as feats? Why must the solution always be, "I never want to forgo anything. I just need more stuff!" Thinking about my own Rogue, I think that I have in fact added the equivalent of one bonus feat to the progression, but backloading it rather than frontloading it because a) at low levels rogues provably rock already and b) the main help martial classes need is above level 10 and c) rogues are already arguably tier 3 or so (and certainly are in my game with increased skill focus).