It's looking cool so far Some Guy, I was thinking of an idea you could consider, you could make it so they've hollowed out the inside of the asteroid (maybe not actually model the interior tho...) and have tube like connections going into the middle.That way you could kind of "chisel" the asteroid away here and there and make some crazy pipe system around it.

Just an idea, hope it at least gives you a bit of inspiration!
Good luck with whatever you decide mate!