Is it immature to want an M-rated Final Fantasy game?

Answer 1

No. Although it's very immature to want a dark and violent Zelda game, it is not for Final Fantasy though. Final Fantasy Type-0 is shown to be very gruesome for a Final Fantasy game and it happens to compliment the dark tone of the game rather than being there just for the sake of appealing to gorehounds. Although if Versus were to have brutal and violent scenes such as Noctis dislocating a knight arm, causing him to scream in intense agony, or Ignis killing a man with a knife to his throat, it would probably end up alienating fans of the classic Final Fantasy games and they would complain that the modern Final Fantasy games are too violent and they are too similar to WRPGs.