I think a hyper would be a good move too, but Thorpe apparently can't exceed 40 meters with this next coaster.
Thorpe have covered:
Dark coaster: X:\
Inverted looper: Inferno
Sitdown looper: Colossus
Dark/sitdown looper: Saw
Family/kiddie: Flying Fish
So what could Thorpe's second tallest coaster be (assuming they build as high as 40 meters)?
The can go to 50m because Swarm doesn't exceed 40m.
IMO the park needs Intamin hyper ala Bizzaro with the twisty turny bits on the island behind the swarm and an out and back bit behind the park. A compact wood and a family coaster and the park would be as good as it's ever going to get IMO.
But even so, 50 meters is still only 164ft. The smallest (not including Hollywood Dream as that's not really the same sort of Mega coaster that we're talking about) B&M mega coaster is Goliath at Six Flags La Ronde
and that's 174ft and its tallest drop is 170ft. Thorpe Park could only achieve this if they then created a 3-4 meter tunnel below the island. That said, Thorpe Park obviously doesn't have to equal Goliath, but do they want to own the second smallest B&M mega coaster?
And besides, a 3-4 meter tunnel constructed below the ground isn't very big so it wouldn't cost Merlin a lot to incorporate into a design. If Tussauds could blast a huge crater for Nemesis then I'm sure Merlin can dig a trench and fill it with concrete so that it doesn't leak or sink.
Edit: Here's a POV
Am I right in thinking that a ride like this achieves between 1600 and 1700 riders per hour?