I would rather they just keep Lost Continent as it is and put something in between Marvel and Toon Lagoon. Why replace one of the most unique lands at the resort with a land that only has seasonal appeal, doesn't really gel with the rest of the lands, and has somewhat dubious cross-generational appeal. I do think Rankin-Bass might warrant representation in the parks, but in a smaller capacity, perhaps with holiday events or mazes.
Lost Continent really just needs its own unique ride and all these ideas for its replacement can go to EU.