Wishes for permanent abilities
Very interesting thread, except for the minor flamewar.
First of all, wishes ARE a tool, that any Wizard, Cleric, or Sorcerer can cast upon obtaining 18th or 19th level. (Miracle referred to generically as wish).
Wishes have very specific stated permanent effects. Mass healing, some ressurection, and attribute enhancement. Period. Everything else "may fulfill" but "may also be limited" by the DM. The reason you don't see this detailed out, is it's hard as hell to detail all the different possibilties, and instead simply say...check with your DM on what seems fair. So, relevant to this discussion, most DM's should have an agreed upon, clearly understood limitations around wish for his players. Failure to do so is robbing the players of an important and valuable tool, and you would be better to yank the XP requirement off, and use it as written, or simply eliminate the spell altogether.
So, in light of providing a valuable resource to my players, we developed a set of guidelines to follow when wishing for anything except what is listed above (magic items, feats, other class abilities, etc.). Without going into the rather detailed version, it simply has the following cardinal rules:
1) The proportion of a wishes' duration is inversely proportional to it's power.
2) Wish is a spell. A spell that affects another being is subject to spell resistance and a saving throw.
3) Wish is ninth level, and requires a sacrifice on the part of the character, and so the power should reflect it.
So, to answer your question of whether or not you could wish for a feat, absolutely. Would it ever be permanent? No. Can a wish grant you the ability to accomplish anything you can conceive. Pretty much, at least once.
I definitely agree that since it is a spell, in the PH, it is certainly subject to being balanced fairly. I have found that permanently giving someone a feat, magic item, or other ability permanently is EXTREMELY unbalanced. I wouldn't recommend doing this in any DnD campaign.
Therefore, in answer to your question of how do I like the structure you laid out? I don't, because I think the potential for abuse is too extreme. Having said that, however, if a player in my campaign wished for a +2 to his Fort Saves (the equivalent of a feat), I would have no problem granting that wish, and it would probably last for a long time (certainly a week, probably a month, maybe a year or more, depending on how time is tracking in the campaign). Furthermore, if he continues to cast other "long term" wishes for benefit of his character, then the duration for ALL the wishes will be reduced accordingly. (Ie, 1 "feat" benefit = 7 months, 2 "feats" = 3 months, 3 "feats" = 1 month, 4 feats = 1 week, and so on).