Small update:

I attempted to get some readings with my Oscilloscope this afternoon and found the output of the 'resistor pack' or 'fan controller' is DC... some noise on the line but appears to be actual DC. I could not detect any PWM signal at all up to 25Mhz, which is the limit of my scope.

So, I think the PWM should work, but I will have to consider short and open circuit protection as well. Back to research. *sigh*