one the things that made me think expansion here would never truly be on the horizon, are all of the work you would have to do to get this land ready for development. If you build into RoA, you need to fill and stabilize that land and replace the water reclamation area you are taking out + whatever else you are required to create as part of the expansion. If you maintain the Belle and the service canal you will need a pedestrian bridge to navigate that. Depending on how you build this out, railroad will require reprofiling, pedestrian over or underpasses, and/or an at-grade crossing (unlikely). Show buildings will likely be outside the rail line and would require elements to get you from the land hub into the attraction building.
If you build something big back there, you can’t make it a dead end. If you loop it back through HM/LS, you will end up with a bigger traffic nightmare than you have now.
Route it behind HM? Then you are potentially talking about expanding the roof of the main part of the park as a hidden bridge over the entrance to the Utilidor system, and (hopefully) a lot of on stage work to mask that that is where you are. Does that mean service disruptions to the system?
If you want to take a bite at this apple, you better take many big bites before it gets all brown and sad looking.