I hope the higher tier spells are really bombastic looking, that's what I think of when I think FF games, big flashy spells. I think for the casters, some extra player animations (that is, the mocap, not the particles in this case) would be nice for the higher tier spells. I.e. For current spells you just wave your stick, but maybe for the next tier you could use a fireball motion or something more dramatic looking.