They could solve a big chunk of the tiering problem by cloning TSM and Soarin'. (Both have been considered but, as far as I know, neither is moving forward.)
Cloning those rides seems like a no-brainer to me. Even with Disney's penchant for ridiculous overspending, neither ride is particularly advanced or complicated and should be able to be duplicated for very little money. Aside from the ride systems, both are essentially just warehouses with a projection screens - how much could that possibly cost? And, they both are easily changed with new movies/programming down the line, allowing two separate rides, if desired.