This has already been done. The Puma HC1 had no torque meter, only a collective pitch gauge.
Problem is, you need to know the CP limits in your head, because they are different depending on the flight regime you operate in.
E.g. the limit was lower in the climb than in the hover (and in the cruise) and again different for underslung load work. They also changed depending on DA.
There was no account taken of transient torque spikes so the limits were probably set lower than the aircraft could actually take.