I'd say to make it harder; it would make what characters you pick more relevant, and you would have to develop genuine strategies for who you fight and how.
Another way that I think it could be improved would be to include more of the world than just the El Nido archipelago. To do that, it would obviously take a bigger machine, at least a PS2, if they were to expand and put as much detail into each place in the rest of the world as they did in El Nido. Imagine how it would be for a place like Truce or Medina to have the same varying areas as they did in Termina. Or, even better, the elaborate things they could do with Porre, and just how intricate they could be with whatever 'castle' place they have for Dalton to rule from.