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.

Ah, good point, I'd forgotten you could push people into things they can't normally do (i.e. backflips.) Yeah, this does sound workable, although I doubt it would work on that sort of scale, unless you found some handy combo.

As for the rebels overthrowing you, well, "this only works on the weak of will" is usually applied to mean "this doesn't work on PCs/important characters." Can't you just picture the great story based around Our Heroes encountering the nascent Collective and defeating their nefarious agents (they could be anyone! Anyone!)

After all, you don't start with the world under control, do you?