...It also saves people having to poop in their rucksacks...
I have humped my share of kit too, so I know where you're coming from, but one can not replace the other. The biggest difference is the time vs quality aspect. In your example where you send an OP out for a few days, you are getting a few days' worth of info. If you bring a UAV for a few days, you are going to get a few hours of coverage. Yes it might be from a better aerial vantage point, but you'll only ever get a few hours (at most) flight time out of the thing at once.
And for the foreseeable future (until it is ultralight and solar) the weight trade off is going to be nil anyway because someone will still have to carry the thing, plus the control station, plus the fuel, etc.
But none of this answers the part about airspace deconfliction I brought up above. The troops never see this part on the ground, but every single NATO-launched anything from UAVs to Helos to Fast Air to artillery shells all have to be kept track of to ensure none of them smash into each other.
If two UAVs smash into each other, now you've got to go send a patrol out to get it. Worse though, if a UAV hits a helo carrying troops it's a tragedy.
It's not like on COD MW2 where you pull out your laptop and that's all there is to it.
Even when the Coys (briefly) had them, there was all sort of 2IC work going on in the background requesting airspace at grids X to Y and altitude Z.