So I'm assuming that it's understood that the 'backlot' area of Hollywoodland is just a blank canvas ready to be turned into something attractive. Honestly, if they razed the entire area and replaced it with a few appropriately themed attractions, I don't think anyone would see anything worthwhile being lost (as much as I love the Muppets and their theater, the attraction just doesn't, well, attract).
The whole Monstropolis Idea and the door coaster is constantly talked about, and while it would fit in with the rest of Pixarland, wouldn't something more...hollywoody work better?
A large-scale stunt show (like Universal's Waterworld, or DHS's Indiana Jones) seems like it would fit in with the era perfectly. Heck, they could make it a western one, and bring in both the Lone Ranger and Zorro, if a movie tie-in is required. Disney did a car stunt show in Paris (and again in Orlando) and did the Indiana Jones one in Orlando (which was quite a bit better than I had expected). Have they ever done one in Anaheim?