I'm more of a ride person myself, but I have been pleasantly surprised a few times (Festival of the Lion King, and the old Tarzan Rocks, believe it or not). I would expect the idea here is that they already have theaters in other parks around the world, and they have theatrical productions running on Broadway and touring, and so it would be relatively easy for them to rotate in a fresh show in the MK theater every few years. You get something new to offer repeat visitors, and plus, as you've said, it would be a nice boost in capacity for a park that needs it.