Some feats are so mundane, or so essential that everyone should get them just for sitting down at the table.
Heighten Spell: If we imagine each wizard spell as a very specific effect with a very specific forcefulness, I guess I can see why wizards might not be able to just boost their DCs by using higher spell slots. But I could argue it both ways. For wizards. For other casters? If I want to blow a high level slot on a lower level spell, why shouldn't the DC be that much higher? Frankly, I don’t see the point in keeping this feat a feat just for the wizard.
I'm not sure I follow your arguement here. Heighten Spell isn't a bad metamagic feat even in the core. It's main problem isn't that it isn't useful per se, but that for any given spell there is usually already a higher level version of the same idea (mind control, battlefield control, direct damage, save or suck, etc.) that does much the same thing only 'better'. Thus, it's rare that you wouldn't use the higher level version instead. This makes the feat really niche. (The same basic problem applies to feats like Empower Spell and Maximize Spell as well.)
How niche I couldn't really say, because in my game you don't add spell level to the spell's DC automatically. So getting high DC's with even high level spells is quite hard, and indeed at high levels you expect your foes to make most saves. 'Heighten Spell', as it works in my game, is therefore quite useful as a way of boosting the DC of a spell (in exchange for a higher level spell slot). Thus, you have the choice of using a higher level spell which is easier to save against (but might have more gross effect if it works) or a lower level spell (heighted) that is more difficult to save against. This makes the feat much less niche.
Power Attack: [And sundry feats that effectively trade AB for damage.] This becomes a necessary feat at higher levels, due to HP inflation, and the way that AB outpaces AC. If you need an in-game reason to wrap your head around, well, anyone can take a reckless swing right? Right.
Yes, but is Power Attack really a reckless swing? Note that it doesn't reduce AC, which would be more to the definition of reckless. Rather, power attack is actually closer to the notion of a 'called shot'. I've considered moving it into a manuever on several grounds, including making it the called shot mechanic, but haven't done so because it so well occupies the entry level point on the strength feat tree and I can't think of a replacement I like better.
If you want to attack recklessly in my game, you take an 'offensive fighting stance' (the opposite of fighting defensively), available to everyone. If you want to make frentic attacks, you declare a 'flail' action - again, available to everyone. And of course, there are feats that make you better at those maneuvers. Thus, I have no pressing flavor need to share power attack around.
Trapfinding: Okay, not a feat, but still very much in the “shouldn’t be” category. Blowing two skill points per level to keep two skills maxed out isn’t enough to even attempt defeating any bizarre trap my DM might throw at me? I need a special class gimmick too? This is like if every monster of 5 HD or higher had “Damage Reduction: Must be a 1st level fighter to bypass.” It’s niche protection taken too far.
In my game it is a feat, so as to ensure that parties can be put together without a required rogue.
Weapon Finesse: I need special training just to aim with my...aim, rather than with brute force? With light weapons only? Get real. Get game! This isn’t a powerful feat; this is a necessary feat for many characters. At least PF doesn’t screw rogues out of WF for two levels, but it’s still a feat slot lost for no good reason.
My basis problem here I've mentioned earlier - you risk making Dexterity too good as a combat feat. You are increasingly allowing a player to dump stat strength for little cost, particular since you are now allowing everyone to essentially start with both Weapon Finesse (convert dexterity to melee to hit) AND Power Attack (convert melee to hit to damage), what do you really need strength for? I've seen people want to house rule again and again ways to make lightly armored high dexterity fighters equal in various respects to melee brutes, but if you do that then they are almost strictly better than melee brutes. You have to let people give up something just as much as you have to make options open.