I feel Dissidia's system worked well with the FF brand, it was all about showing off flashy attacks and projectiles in 3D and it was pretty simple and easy to use unlike most traditional fighters. If it had to be made into a more traditional game, I feel ARKSYS (Guilty Gear/BlazBlue) would be the best, simply because 3D fighters like SolCal, Tekken, and whatnot don't have the mechanics to implement spell casting/limit break flying shenanigans that you would find in Squenix's franchises, and would seriously limit the scope of the game and the characters needed. 2D would simplify this and make it easier to implement. It will take me awhile to determine who the roster should be...