I didn't think the fighting styles were unbalanced. They tend to be very difficult to qualify for and very specialized.
Is the fighting style in OA that changes the monk's damage from 1d20 to 4d6 unbalanced in your opinion too? That a 3.5 damage increase on average.
A 16th level character who sticks with fighter to get 14 feats should get some sort of bonus on par with someone who took a prestige class.
The wis requirement is poorly worded IMHO. I think you are supposed to be able to learn a number of different styles equal to your wis but since each style requires exclusive dedication for so many levels it is all but impossible to qualify for more than one at any higher than the first rank.
You don't need feat chains containing 10 feats. If you put in that many feats you should get something for free.