Umm, yeah since you cant make a ring, why not make a map that looks like it? and perhaps missions too?
Ex;

Here is a good map that could be made into trem... This would be more like CTF, but I believe would work for Trem, 2 outposts close to each other...

For missions, could be simulated ship sorta situation like here:

The point of this map would be like... Escaping before the tyrants or w/e get you... so its like an obstacle course... also what makes this hard is you have limited resources to start with... Ex; 2 Spawns, no reactor...
& you have to get to the safe spot, where only wallcrawling will go, but for humans you get there by teleport from a spot or something... I dunno...