Yeah, I'd ignore me on lighting. I do tend to take things a little TOO ambitious.
3d printing sounds like an awesome idea. Definitely interested if you manage to get that to work.
Rock/asteroid probably is the easier way to, and gives you a solid base. If you a "too ambitious" idea though......if you're planning bridges, just make it ALL bridges. Bridges over bridges over a bottom level of brudges.
Over a black, maybe space coloured floor.