I always thought USF could turn some of the park's rides to horror theming.
Simpsons becomes Treehouse of Horror.
Despicable Me turns into a haunted house.
Twister becomes a horror/B movie shooting gone horribly wrong (scare actors, etc)
Shrek and Lucy get removed for a year round Monsters family dark ride
Beetlejuice gets a special Halloween edition.
Disaster becomes the Terror Tram like it used to be (theme it to a classic horror every year - Halloween, Nightmare on Elm Street, Friday the 13th, Alien, The Thing, Hannibal, Psycho, The Birds, It, The Shining, etc)
Diagon stays the same, but a simulated Death Eater/Dementor attack every 10 minutes. And a special scare zone in Knockturn Alley (you get "trapped" in by scare actors briefly if you aren't careful - might be crazy and lawsuit friendly but it would be scary)
Bill and Ted stays the same
MIB gets themed to a hostile alien invasion (vicious aliens, a few blackouts, more fog, jump scares, spinning, etc) but mostly stays the same
Springfield is mainly a light hearted creepy carnival with Halloween decorations primarily.
Animal Actors hosts something like Goosebumps or Are You Afraid of the Dark? - maybe even Casper or Scooby Doo? Something more playfully spooky than terrifying.
Barney could host another Halloween show? Coralline maybe?
E.T. stays the same
Rest of KidZone is a ?..
Horror Makeup and T2 could be open for HHN as is.
And instead of multiple houses (5-6), Uni Creative could focus their efforts on one terrifying, large, immersive haunted house that is consistently stellar.
Scare zones could be the same. I know my idea would require closing a lot of rides down for theming, but a lot of them could be done over a weekend (Simpsons, Beetlejuice, MIB, Despicable Me) since you'd just have to make minor changes. Terror Tram, Twister and the two new shows would be difficult since they'd almost be from scratch
Just a crazy idea that might open up expansion space for both parks since less soundstages would be used if they focused on making one amazing haunted house a year rather than 5-6 ok to decent ones. Plus, the rides are pretty high capacity and you could have the overlays run during the day too