-Multi launch coaster.
Yes we've got Stealth, but modern day launch coasters are so different to Stealth. Have it as a lower-to-ground, not-as-fast ride with a long layout, and it'll be a winner. Something like Manta at Sea World Abu Dhabi would be incredible at Thorpe. But also the likes of Taron, Taiga, Helix, etc etc. Any smaller version of those would be *chef kiss*
-RMC. A balls to the wall RMC hybrid or single rail would be amazing to have in the country. Would it be the right fit for the park? I'm not necessarily convinced. But from an enthusiast wet dream perspective, absolutely.
-Vekoma tilt. The gimmick sells itself, and is different enough to anything else on park. But the real kicker is getting a modern Vekoma on park, which are wicked fun. A bog standard Vekoma sit down coaster feels unlikely at Thorpe, simply due to it not having the USP. Chuck on the tilt gimmick and a fab layout though, and they're golden.