so you want to add to the complexity of the TR system, adding weight and more potential points of failure, into something that already has a low probability of failure in any form, just to guard against an even more remote type of failure.............c'mon chopjock- get real!
If you have an un commanded stuck full pedal and you don't have easy throttle control or perhaps a bird strike on a tail blade causing severe vibration with tail rotor imminently about to fall off etc and high up in the cruise, how do you maximise your chances to land safely? Presumably this is when you do not want a turning tail rotor? Just for discussion ...