I imagine Uni would want to either use the Classic Monsters to fill the Black-and-White style again or use those movies as inspiration for originals a la Nosferatu and Hive. But they are definitely good ideas and it would be real cool to see some representation of non-UCM OG classic horror.
I worry that the Disney/20th Century merger officially kills any chance of ever seeing a Treehouse of Horror overlay or zone for HHN. It's a real shame they never went through with it while they still had the chance, they could've had a lot of fun with that style.
The minute someone talked to me about the idea of Pan's Labyrinth becoming a house, I was on board. It's definitely not full horror, but the Del Toro elements and designs would work insanely well in a house. The Pale Man is the obvious win, but Pan, the Mandrake Root, and even some of the more grounded human elements would work pretty well too. I could definitely see it fitting into the house lineup similar to Trick R Treat. Cult movie with some very interesting setpieces and designs. Probably a little more on the atmospheric side like Us. B79 would work real well for it.