Llanelli, had a read up on brushless motors and yes IF batteries can be improved I can see it would be the path to follow. I can see a problem regards the speed of the motor re the wieght. A low speed motor would require large conductors so the weight would be high, high speed motor lower weight but a gear box needed to get to, say, 400 rpm. So your back to the same problem.
All this worked out by an old brain feed on a bit to much red wine, so I wouldn't bet the farm on it.
The more I think about it the jet tip is well worth looking in to, no MRGB, as we know it, and no tail rotor system. I would say a bit more noise well worth the extra safety.
Now I guess I'll have read u on tip jets/bleed air, tomorrow, a clear head needed.