I like the system that awards you for doing actions, it can be abused, yes, but if you have the patience to do it then good for you, you deserve to reap the benefits. It's no different than if someone were to power level in a normal Final Fantasy. Since Tactics battles take longer, it makes more sense to have the progression of your abilities effected by each action, not a lump sum at the end.

That was actually one of the things that somewhat irritated me about Tactics Advance, the AP system.