Actually, if the Imperius Curse grants the victim the abilities necessary to carry out tasks (which I had also forgotten about,) then it seems more likely to me that it would actually require some degree of micromanagement from the end user for every step in the chain. It makes it seem more like they're actually investing some of their own mental power rather than just applying some suggestion, and there should only be so much of that to go around, which could make creating an army of imperiused slaves an impossibility.