It would be easy to conclude that it's a maze, what with Thorpe's eternal love of mazes. A maze would suit anything that Derren could come up with, especially the "re-rideability" of the attraction. But we know that it's a major investment, so it certainly won't be a maze.
Whatever the attraction is, it's bound to be quite trippy, thrilling. There are no tracks, but there has to be a way of moving around the building that presumably is more sophisticated (more expensive) than using your legs. Has anything actually gone inside the building yet? I like how they chose a specific brick, with those dark speckles. Clearly there's some thought behind it.