Guess give the main characters personalities, but keep everything else the same. Still have the choose your party thing at the beginning and have different endings depending on whom you have in your party, but still keep it so you'll be still be able to pick more than one of the same character, so you can still have a team of 4 White Mages if desires.

Guess make it sort of like FF 3 DS but on the 3 DS or 4 DS or 3 DS 2 or something.