I will just pick 1 stage from each. # of * out of five for priority

I. Underwater cave maybe *
II. Pirate ship at sea perhaps. *
III. Crystal tower****
IV. The underground mantle place with the lava*****, (can't remember names)
V. The Big Bridge*****
VI. So many places...
a. Phantom Train****
b. Floating continent****
c. Opera house*****
d. Figaro castle**** ( moves to different background )
VII.
a. Old shinra from advent children***
b. Church ***
c. Gold Saucer****
VIII. On the Ragnorak in Space******(I don't even like 8, but that would be awesome)
IX. Library, perhaps even in a book***
X. Blitzball stadium***
Everything else they added apply here.
Mostly off the top of my head, add, comment...