Better Designs and are we happy about this
It depends on what engines are being used on the helicopter, most of the ones I see are jet engine powered so their exhaust is substantial so maybe that would work.
More important consideration is are we happy about these unmanned helicopters or any plane for that matter flying over populated areas, (not in war zones). I'm a glider pilot and in the UK the CAA has proposed that all light aircraft, gliders included, should carry a Mode S transponder so that collision avoidance systems on commercial aircraft and unmanned aerial vehicles can detect and avoid us when flying in uncontrolled airspace. It's a worrying trend.
Especially worrying for Glider pilots as the equipment costs nearly as much as some gliders, will need much more electrical power. It provides no benefit at all to us so we end up paying to help make Commercial Aviation more profitable.
BTW - Us Brits are some of the best competition glider pilots in the world, judging by the gold medals we win every year (just thought I'd say that :-)