Saurabraten has a map maker where players enter, place blocks of material as like with a ckit or in minecraft. The idea using the Cube and Cube2 engine in saurabraten enabled almost anyone to make a map fairly easily and quickly. I don’t know how easy this would be to implement, but it would enable almost anyone to make a trem map.
Alternatively TimeSplitters which used Id Software’s Quake3(I think) engine had its own in game map maker that you could use with an standard PS2 game controller. It should be possible to implement something similar here. (I am not sure how difficult that would be)
Just thought I would spam off a few ideas.