for starters you could simply have a similar system to regular melee. just to make it more simple you could make it minerals or gas only. have each site have unlimited amount of stuff.

this gives the other team something to harrass other players with, giving the game more depth.

there are all kinds of things you could make players do to build certain units. ei: control a certain point on the map for bigger units, which would be protected by large creepies or something. otherwise do like melee and have similar reqs. idk there are a ton of things you could do.

New terrain, this was a bitch to do lmao

looks very polished. good job!