Not sure if this is the right place, but.....
I've never been a big fan of AoOs. As other people have written, I feel they tend to slow combat.
While I don't go as far as many of the fighter advocates, I do think they need a little extra.
Therefore, why not require a feat for players to make AoOs and give fighters (and the other martial classes, if you like) the ability as a class feature?