I don't think the dynamics of the mass moment being above the electric drives is necessarily a problem. The two necessities for electronic stabilization are that the drive moments are sufficient and that the electric drive dynamics are faster than possible plant disturbances. So the rate of spin up of the electric motor / prop system will need to be significantly faster than the rate that the broomstick can tip over or otherwise be perturbed by aero effects. The need for fast dynamics on the electric drives, in fact, argues for high disk loading.

The amazing effectiveness of electronic broomstick stabilization is routinely demonstrated by the various two wheel inventions that people zoom around on these days.