I had a thought; with the recent reveal of the Uncharted coaster at PortAventura, which seems likely to be an Intamin Multi Dimensional Coaster, could Project Horizon be something similar?
I know that Alton Towers technically already has Thirteen as an Intamin Multi Dimensional Coaster, but the model has evolved in scope quite considerably since Thirteen was built, and a ride with a heavier dark ride focus and different trick tracks (similar to Gringotts, or the ride that PA are seemingly building) would certainly differentiate itself well from Thirteen. A roller coaster with a heftier dark ride element would also arguably add another dark ride-style attraction to the park (which many argue that it needs), and I also feel that it could suit the smaller ground space better than a flat-out coaster.
If this ride were a coaster with a heavy dark ride element with some higher thrill coaster portions scattered within, it would make the height make sense while also fitting a decent coaster within the space (if it had a heavy dark ride focus, it likely wouldn’t require as much space as a regular enclosed coaster).