I actually think Oz would be a great expansion for Epic Universe. It’s possibly one of the most famous universes in film and I think being able to walk through a portal into it would be really cool.
Oz and LOTR would be excellent additions to EU as those are both franchises that require complete immersion (or at least something close) that a land which can only be accessed through a portal would bring.
In an ideal world, I think USF should become to park for legacy as well as urban-centric properties, IOA should be the park for the action/adventure properties, and EU should be the park for hyper-immersive properties that require their own ‘universe’