Grav,
Yeah the rotation helps a bit too! Actually I was envisioning a system like the one you described with a feathering bearing and some sort of collective pitch control on the rotor but using the variable thrust in place of cyclic control. As you said it may make for a survivable rate of decent but I don't think I would want to go out and purposely fly an aircraft that provided no controls during an auto. It may be workable for a UAV though but you would still have to worry about what the thing would land on in case of a power outage.
I agree with you on the kit type helicopters with fixed pitch rotors. I remember seeing one that had four small engines driving two fixed pitch coaxial rotors. I guess the idea was that an engine failure would only cause a 25% loss in power leaving enough to find the ground safely. I guess everyone has their own take on that risk assesment but I don't think the trade off between less complexity and safety is a good one in this case.
Max