I would love to see a game where you can build your own coasters, or even a game where you can "ride" pre-made coasters. I don't know what roller coaster tycoon is though (I've heard of it but never played it). Is that more like a simulated theme park where you make decisions to make money etc?
Interesting idea building roller coasters!
I have done train sandbox games but a roller coaster would be cool and more interesting for younger players that probably have never seen a train or played with train sets.
I may have to try something like that.