Does Final Fantasy VI really need a remake? Outside of cosmetic issues like graphics and sound, I can't think of what could really be done to improve it. Same goes for most of the older (pre-PS2) FF games, really.
If any FF needs a remake, and not just some touch-ups, it would probably be VIII. I enjoyed most of the game, but the draw system is, at best, a "noble failure." If it could be replaced, or at least somehow made less tedious, that'd be great. Maybe something like Final Fantasy Origins for the PlayStation, where you could choose at the beginning of the game whether you want to play with the original or the revised rules?