I really don't think it would have been a musical. If anything, it would have been an opera. Having been to the Met Opera several times, I can provide that operas are very serious and emotional. It would be perfect for the kind of game Final Fantasy XV appears to be, since operas are almost always very melodramatic, and so are Final Fantasy games. But I imagine that it'd be tough to make a good opera that's long enough to keep an RPG interesting.