I think it'd be a nice touch for damage numbers to be accompanied by their respective element (if there is one). Obviously not the most important feature seeing as resistance stacking really doesn't matter in this game, but would still be a nice touch.
And of course, the ability to toggle it on/off.
And this would only come up on damage you take.
I'd be happy with a distinction between physical and magic damage text colour, for self and enemies.
It would've made more sense before 2.0 when elemental damage was actually a thing, now it would serve little purpose other than "it looks cool".
Request: Remove elemental resist materia
Knowing the Difference between Magic and Physical dmg by giving them different colors would be helpful.