[Hectic]

id also say an aep is prolly yer only option. They are light enough to not cailuse too much issue with a larger sized chopper and you could likey invert it to use a hopper type design for ammo as opposed to the low cap spring mags they use out of the box. Would be prety neat to have an "uav" witu a cammera( thays been done) as well as some fire power.
you may also look into the RC tanks that shoot airsoft bb's and see what they are useing in those to shoot tue bbs with.
or another thing that may work would be just to have a small container that you could remotely open to just dump bbs out of like a bomber. Use some heavier ammo like .40's and even from a lower height they will feel the impact and if the delivery system had a small enough opening like a lil door that becomes a small ramp you could sort of stream the bbs out in a line to cover a larger area with them.
good luck with yer idea!