There are a couple of games out there that have tried the whole turn based MMO stuff.

Wakfu was something that they tried out but then pushed to another company (I think) so they aren't really touching it. Turn based MMO on how it could work.

Atlantica, which was a game on steam, made you have your own party to control while in an MMO setting, but isn't exactly turn based like FFT was.

There are options out there to show that they're feasible. Now, would the FF IP make the game more successful than the two others? Maybe. I would love to see them try it. FFT was one of my favorite MMOs and if Wakfu was their test drive, FFT should be feasible to be done with a few tweaks.