I couldn't innovate to save my life, so Good Luck and Best Hopes to anyone who can.....but,it seems to me,that current electric set-ups with 2 blades,fixed or Rasa-type,already have whatever you could want,in terms of thrust, braking, and lack of noise.
Just my opinion, of course, but where improvements could still come, is in the area of countering the effects of the inevitable spiral air flow off any rotating-blade-type propulsion system.
So, flow straighteners/canalisers/shaped bits on the fuselage, or simpler/much cheaper contra-rotating blades(than those used by Mr. Silvestri for example) without too much loss in efficiency, might be a more likely route?