Prehaps a tilestype option could be implemented on a Per-Level basis. You would have to load a tilestype for the level you are on. It is saved inside the .nw levels or graal levels (If you do change it) You could make predefined tilestypes to load for your level and stuff. I think it would be worth it overall, and make it better to organize new tilesets.
Saving it inside the level itself would be benificial becuase you'd have to change the level to hack the tilestype
Rather than makeing some script command similar to addtiledef. It will make it a little harder to implement a new tilestype serverwide, but it will prevent hacking, which is good.