Graviman,
If this is getting too far off topic, please say so.
Your knowledge of electricity is far above mine, so I get to question you.
Mass/Torque:
An electric motor that is extremely fast and small has an advantage. However, the helicopter rotor is a large disk with insignificant thrust comes from its center. Why could not a reasonably large diameter, linear induction disk motor be an integral part of a special rotor hub, which is shaped like a very large Frisbee? It might have thousands of poles (with 50% or 33% of them activate at one time) and air bearings to maintain the gap. The weight will be kept down by the preceding integration, composite construction and the elimination of the gearbox.
To double the motor's speed on coaxial helicopters, the motor could be located between the rotors, with the 'armature' connected to one rotor and the 'stator' to the other rotor.
Potential Intermeshing failure:
What if triple redundancy was applied to all facets of the drive. In other words, separate batteries, motors, and controls etc. Electrical systems are very reliable, but, if one system went down, the other two would probable still provide slow level flight.
The large electrical force and its large moment arm should be able to maintain rotor inter-phasing, considering that CNC milling machines can inter-phased multiple motors to within a 10th to 100th of a degree.
Just a demented idea.
Dave