The ducted fan might be an option what with the availability of powerfull and small motors and light battery packs. I see this built into the fuselage back with the tail. It would only need a few ounces of thrust to have a wild effect. The radio could be run off the BEC part of the ESC. And you'd have to find a boat or car ESC with polarity reversal. Either that or duct a heli tail rotor in there, run the motor full out all the time and control the pitch with a spare servo.