The obvious IP for me that stands out is Lord of the rings/middle earth themed area and rides.
Massive fan base, huge potential for rides based on landmarks from the films.
Obviously I already know the issues for why this hasn't been done it's just difficult to believe they haven't been resolved.
Also hugely surprised we haven't seen an IRONMAN themed ROLLERCOASTER. I know we're getting that simulator but Ironman/Downey Jr is the main draw of what is currently the biggest franchise in cinema. Avengers potentially going to be at least top 3 box office draws of all time and obviously Ironman would be easy to adapt into a coaster
Also to add, not sure if this does exist at all, someone correct me if I'm wrong! A Nintendo themed park. Popular characters like Mario, Donkey Kong, Zelda, pokemon, sonic etc