Could do with a bit more detail. Do you mean they could add missions at nearby stations to supply some of the commodities required for a colonisation construction? Would that mean that even if a player did nothing at all their construction projects might get completed eventually just by others players doing those missions or would the system architect have to do something in order to make those missions start appearing. One question on my mind is, how would I prevent those missions from completing the constructions in my system that I want to leave as unfinished race tracks?