If space engineers were to get a more cohesive solo/coop survival mode without having to juggle fifty possibly incompatible mods it'd be a real killer app. There's potential there, but there's a bit too much manual scenario/server setup and once you get started there's not really a lot of progression outside surviving long enough to get a basic smelter + dirt drill system set up.

That said, I recently had a surprisingly good time with the Wasteland Scavenger mod, which sets up a pretty unique scenario where you have to salvage a lot of components from POIs, you can't build things like tanks or thrusters yourself, but you find them lying around in bases and wrecks.