...someone with more money than good sense bought four of those high tech brushless motor, high voltage LiON electric mowers, gutted the motor and ESC from each one, fitted the motor up to a sturdy airframe, then added a NAZA or Pixhawk FC, GPS and radio.
For example, the Kobalt/Greenworks Max mowers have an 80v LiON system and brushless motor, pushing a 22" heavy steel mower blade through grass and weeds. Surely that system would have sufficient power to push a 16 or 18 inch rotor (20"? 26" even?) Four of those working together would give you a drone with a potentially mind-boggling payload capacity.