AIE is an alright show, but I understand why it isn't as popular. I personally wouldn't want to devote that much of my day to perform, not that I would want to sing in front of people anyways.
While I would like to see original attractions as well, using a WWOHP (an existing franchise) reference doesn't really work. If we got an attraction of Spiderman quality you wouldn't take it?
My understanding is that no character used at IOA can be used at WDW. That would CA as he had the diner and I believe that Iron Man and Thor are represented in the big cutouts.