Here is what I think would go over big in the area that was PI. A Boardway type show that brings many of the traveling Disney shows to WDW. I know I would go every time there was a new show.
I also agree that Disney needs another dinner show. Love HDDR, but would be nice to have something new.
There are three dinner shows (at least) - HDDR, the Luau, and Mickey's Backyard BBQ. Not that I'm saying we're oversaturated with diner shows, but HDDR isn't the only one.