(Warring Triad) Godess Phase 1 music

[Konicorgi]

I don't see the problem with that + they can remix the theme
Calcabrina's theme is slow and creepy, it fits perfectly the fight

Calcabrina's theme IS made to be slow and creepy. Just like in FFIV (and I was disapointed to have the classic boss battle following instead of FFIV boss battle theme)
Celes' theme is made to be sad and full of feeling, not for a god-like creature summoned to go to war
Fanservice is a good point, but there's things that shouldn't be done. And I don't see why you wouldn't all the 3 primals of the warring triad to start with the same theme and then have their own theme in the 2nd half. After all, "Battle to the death" is their signature's theme in FFVI, they all share it (along with ultima) and it would make sens to do the same here, with their personnal them following (something rock or jazz as usual).