So, I've been trying to make this work. It already works, BUT - and that's a big BUT - while running around it continuously reassigns the construction orders! So if you have one belt ghost you're running towards ALL your bots will fly out with a belt in hand, the first one places it, and then all return at once and drain your batteries/fusion reactors.
So I'm still thinking about how to solve this. Only reassigning entities that come newliy into range is also not a good idea, because if you don't have enough bots and there are more entities to reassign in range, those not-reassigned entities won't be reassigned until you run away and come back again...
I don't know yet, how to find out which bot took over the job. If I can find this out, I think I can "automate" it.
All the best,
Chris