How high a frequency do you have to inject for sensing? Much higher than the power chopping frequency, presumably. Megahertz? Harmonics from the PWM drive are going to interfere. I can see why separating signal from noise is a problem, and why mating a motor and a controller isn't going to be plug and play.

Larger drone prop motors seem to be mostly permanent magnet brushless. Often the stator is on the inside, and the rotor is a rotating shell carrying permanent magnets that fits over the stator. 12 coils and 14 permanent magnets is a common configuration.

Other drone motors look more like standard motors, with an outside stator and an interior rotor. Some of those are definitely permanent magnet.

Here's a good overview.[1] If you wanted to repurpose such motors for industrial control, the main problem would be cooling. They're intended for use with the prop blowing air through them, so they can dissipate much more heat than most motor configurations. Slow speed, high-torque operation would probably overheat them.

[1] http://www.barnardmicrosystems.com/UAV/engines/electric_moto...