I do think that Colossus will be gone after it turns 20 or before given it's issues at the moment. For 2024 I can see a B&M floorless going in that spot - and slammer's. It will still be a usp unless another U.K. Park gets a B&M or an x-car.
I would leave x because I think that a Chiapas style water ride would really fit in that space as well as replacing Storm Surge and the west beach. The Aztec theme I think would really work.
2018 - SW8, Icon, Rookburgh, Valkyria, Energylandia, Toverland, Steel Vengance, Twisted Timbers, Hangtime, Railblazer, Slinky Dog Dash, Time Traveler, Electric Eel, Wonder Woman...
Which will be best