Assuming you are refering to Menken's Hunchback, I completely agree and I'm not a big Disney animation to stage musical production fan. There was a plan to bring it to the US (after Germany) and I wonder why it stalled. The score, the songs, and the orchestration in the animation are amazing. "Out There" gives me the goose bumps. With the right book, good actors (sans the gargoyles...too cartoony, don't you think?) and the right stage and lighting design, this could possibly do quite well. I'd see it on preview night. Tom Hulce was excellent in that recording but Demi Moore in the speaking voice? What were they thinking?
Now, for the stage actors (no stunt casting, if Buddha permits):
Quasimodo - I'd vote for Norbert Leo Butz
Frollo - Brian Stokes Mitchell can be an excellent Frollo. But Tony Jay can reprise the role.
Captain Phoebus - Matt Bogart or Eric Kunze
Esmeralda - Christine Andreas (too old?) or Rachel York but I think Lea Salonga can be perfect.
"I love acting. It is so much more real than life." Oscar Wilde
"After silence, that which comes nearest to expressing the inexpressible is music." Aldous Huxley