[PvK]

Yes it would be good to be able to upgrade single facilities. It would also really help (in some mods, anyway, which have different costs for different levels of facilities) to be able to upgrade not only to the highest available level of a facility.

I don't think I agree with the comment that "Being able to build more than one facility at a time would make ringworlds and sphereworlds actually useful." Certainly those things are already extremely useful, once they are actually completed.

PvK