Thanks for the replies, I will post the results once I have tried it.
I think I will try darthviper’s method by disabling shadows and minimizing cone intersection, as it requires the least amount of work on my side ^^
The problem with a skylight is that it also illuminates the planet in the background, which should only receive light from the sun - is there a way to prevent that?
Also, I do not think that I can bake the lights into the texture, because each modular mesh is generated from a voxel volume at runtime (so in the above pictures, the room is constructed from about 10000 voxels).