Thanks for the requirements and use case. How about a Gofundme to start on development? I also see a group providing drone attack services along the lines of booter/stresser DDoS providers (distributed denial of services).
On the other hand, I think it will be a long time before visual face recognition will ever get this good, especially out in the real world with bad lighting, hats, eyeglasses etc. But let's say the world of the video authors comes true. What do we do?
Defenses:
1. Microwaves can fry electronics. A system wouldn't need fancy targeting; just blast powerful microwaves in all directions.
Downside:
A. Microwaves this strong are bad for people too.
B. All it takes is 1 anti-microwave drone to slip through and disable the system.
C. Asymmetrical cost of offense vs. defense
2. Lasers can fry the optical sensors used by the drones
Downside:
A. Probably would need a fancy targeting system?
B. Same problems as microwave defense 1B and 1C.
3. Something along the lines of WW2 barrage balloons. A network of suspended lines designed to entangle the drones.
The lines wouldn't have to be very big; a piece of strong thread could get caught in the rotor of a drone and disable it.
Downside:
A. Wind gusts
B. How do you suspend the thread?
C. Do you carry one with you when you go out to Starbucks?
D. The thread would have to be small enough to not be detected by the drone's camera but big enough to cripple it.
4. Ski mask. If the drone is programmed to attack specific individuals using facial recognition, take away it's targeting requirement.
Downside:
A. Maybe drone deployers don't care about a specific target -- just body count.
5. Play dead. It's assumed the drones wouldn't waste resources on targets that have already been attacked, so just emulate a victim.
Downside:
A. Big assumption
6. Wax museum defense. Have a mannequin with target's facial features. Drone attacks wax dummy.
Downside:
A. See 3C, 4A
7. Obscure the target. Throw a blanket over the target.
Downside:
A. Time to deploy.
B. Darn. Left my blanket in the back in the ....POP!