Well, you could allow ;
I think creating a feat chain that ends in an even bigger payoff might be a real good possibility. Maybe another feat something like 'pounce' for a pc given they have taken improved charge? Extra attacks... Now fighters will be lining up to take improved charge!
- movement through allied sqaures
- movement through difficult terrain
- Extra bonuses to hit and damage
- Maybe extra movement in conjunction with other feats like Spring Attack
- ability to ignore readied weapons