From the information that I have and my readings about M383 & M592, rpm value should be measured directly from crankshaft signal, then RPM limit seems to me, be calculated from crank and adapted with other variables like cam & vss. Those are my thoughts.
Then based on that altering RPM values or linearization should affect everything in ECU, as you said, that could mess up whole ECU behaviour.
Do you know which address on m592 are for vss signal multipilier? My theory is it limits the speed per gear (in turn limits rpm). So cutting the multiplier in half could, in theory double speed limit and rpm limit. Assuming it doesn't throw a code based on the wheel speed sensor.
Couldn't find anything similar on the m592 using the m382 or m383 map info. 4 1x1 maps on the m382/383
