i'm no designer by any means, but one would think with all the smarter people out there, a swivel could be designed to rotate, yet resist free rotation. All it has to do is slow the spin caused by rotor wash and spin before the cable balls up. those are two values that can be determined, and in my humble opinion, a value that can be adjusted for.
We have had roller wheels in our shoes, eyeglasses that automatically adjust to the light, and light switches that clap on and clap off for ages. Can we get a swivel that does more than freewheel uncontrollably??