If you want to kick butt in athletics, take Skill expert for Athletics.I don't really see how having a fighter be able to have a +8 at level twelve would change the game. They would hit a little more often than the other classes, and their damage would increase by +3. Oh, and they would actually kick butt in athletics, like they should. Now, if you have a dex based fighter, that might cause more inflation than needed. But adding a few extra plusses seems like it would tamper down some of the complaints of the fighter not doing enough damage (even though, in reality, it is on par with other melee classes).
If you want to deal more damage, take GWM feat or Dueling fighting style.