The Belasco is too small for what I imagine is an expensive show to run. I would eliminate it completely.
I agree with everyone who said that it needs to be in a theatre that is ornate to begin with, so it fits in.
My first two choices are never going to happen: the New Amsterdam or the Majestic (could Phantom move to a smaller theatre or does it need a huge theatre to still have good grosses with a lot of discounting?).
Failing that, my next choice would be the Winter Garden, which I have always thought of as having a huge stage, whether that is the case or not. Probably from seeing Follies there, which was also a huge show...although maybe not really in the sets department. I like the idea of it being right on Broadway as well, as this looks to be an over-the-top elaborate show (hopefully, really good as well). The School of Rock seems to still be doing decently, so could be an issue, depending on when it wants to open.
Next would be the Hirschfeld, which is a very unique theatre to me. There is something about its design and look that I love...whether it is large enough is a question. Again, I assume this show will have a large weekly operating cost.
There is always the Broadway if King Kong does not succeed...again, when does it want to open?
Please not in the Marquis. I hate that theatre. It is so drab, though not as bad as the Minskoff.