It would be nice of materical would be in the game and let you customize characters in certain ways. Not necessarily in as great detail as FF7 let you, but you could be able to equip a limited number of them to gain certain attacks or effects.

The effects shouldn't be game-breaking I guess, but they should be noticable. For example, you could have Restore materia which would make you regenerate health a tiny bit faster when the character was swapped out in tag battles, or vitality plus to gain a tiny bit more defence, or hp plus to gain a tiny bit more health.

I also want all limit breaks to return in one form or another, either as a bit more difficult to execute combo finishers, or as gauge-using supers or mini-supers.

I really want satellite beam and finishing touch as well, for example, in addition to their lv4 limits.