Director: Hiroyuki Ito
Composer: Yasunori Mitsuda
Go back to being a bit more lighthearted again, it's what FF does best. VI, IX and XII all had a less moody atmosphere than X, XIII and XV. For that matter, get a main character who isn't serious all the time again. Gotta strike a balance between mellow when the going's easy and serious when the going's tough.
As for medieval vs modern vs futuristic or whatever, honestly I don't care that much, just actually utilize it well. Don't make it a super high tech setting or modern and then have you away from all that, in a wilderness that could be medieval for all intents and purposes, for 90% of the game (XIII, XV barring the car)