There are several factors that go into the slowness in switching right now. The hardest one to remove is the load time, but many of the difficulties you face when switching aren't part of the load time... it's just very inconvenient. This could be helped/fixed with some more thoughtful design around loading, but in the meantime... you're aware that you could append layouts to other layouts and then switch between them using Page banks. MD gives you 8 banks of 6 pages each, so really... most of your Omnisphere stuff could go in one layout. If you do make a giant layout (via appending) and it works, please share it with the Community.
Thanks!
Dan