I'd bank on some sort of coaster for sure. But as a second ride, this would be a great opportunity to do escape from Oogie Boogies. It can be either a trackless system or better yet a system where you can start by going though some iconic Halloween town locations and end with a thrilling coaster escape from Oogies lair. This way nightmare b4 Xmas gets it's ride that it so deserves. And it would make complete thematic sense for the land.
Yeah Nightmare is kind of a tricky one because Jack and Sally very much go with the spooky / Halloween vibe, but they’re actually heroes not villains. Bringing Oogie in as a way to showcase all the characters would make sense though.