I'll admit, I'm bias with this kinda thing, my favorite Final Fantasy games were 5,6,7 and Tactics, the rest I either hated or have yet to get into the remakes. (8-13 I hated for the record). So I think Final Fantasy as a series should stay more traditional, it's nice to see a game evolve sure but drastic changes call for a title change in my mind.
However other titles like Kingdom Hearts is just a big pile of fanservice that fail in their attempt to make something storywise happen in a sane manner. Especially when a 10 year old with a key can beat a man with a giant sword and who basically killed a God. Then again you have these people interacting with Cartoon characters, most of them have taken a mallet to the skull and are no worse off so continuity goes out the window in favor of fan service, which just bores and annoys the crap out of me. Maybe that's just me, maybe I'm the one who's just not seeing brilliance, in anycase I'd be happy to never see another one again...at least in my room, not going to wish doom on a series that has a lot of fans. ...Doom on you Kingdom Hearts, doom on you if you enter my house...fnar fnar.
Trying to revamp the FF whole series would be a big change and I feel that if you're going to change something drastically, call it something different. All Final Fantasies are similar, but going all out