It's possible to only draw with certain tilesets in specific positions using a GS2 functions, but it's super fiddly to setup and half the time it won't work properly (e.g. automatically flickers back to the default tileset) so I don't really think that's an option.

From what I can understand though, you want an option to switch between 2 tilesets. I don't really think this is a good idea since you should never give the player an option to influence what a level looks like on their screen. It should be the same for all players.