FH 1100, I am glad misunderstandings are cleared.
You can avoid rotor/thrust coupling, as you call it, by having Centre Thrust Line (CTL).
Then the prop thrust offset is not compensated by rotor thrust, and by power out
(you are right, gyros seldom use certified engines), you don't have to
compensate for loss of one of the forces in the system.
RAF accident rate is caused not by material failure, but by inherent instability,
comparable with "tail heavy" FW.
You have to be really trained and fast to compensate for turbulence or engine out.
I assume, you are helicopter pilot, so you are used to fly "inherently unstable"
machines, but you can build a stable gyro, that will forgive pilot errors.
And certainly zero or negative G is an absolute NO/NO on gyro.
Teetering rotor will loose rpm, start flapping, take the tail with it, and you are toast.
There is nothing else to keep rotor turning except the airflow down-up.
If you stop that flow, the rotor WILL eventually stop.
Fly safe.
