then the torque reading should come off the transmission and not the engine
which it does.
The torquemeter instrument whether it be in % or PSI or whatever is calibrated to indicate the limits of the input to the transmission. It is all part of the "transmission" of power it just happens to be in the engine for lots of good reasons too long to list here.
B222 230 430 etc though have a MAST Torquemeter.
The scenario you quote MAY only be correct on certain types of aircraft. I wouldn't go pulling that trick in a Bell medium twin. 2 engines through ONE input for everything.
Sounds like you need either:
a) a bigger helicopter
or
b) less weight in the one you have
or
c) a stabilised turret camera
or
d) all of the above.
Read your RFM regarding the use of TOP. It has speed limitations.