Apparently I missed this topic, so this is coming a little bit late...
Yes, you can use PWM outputs with an appropriate RC low-pass filter to simulate analog inputs. You can even try to hook up a digital meter directly to PWM outputs as some of the meters already have a low-pass filtering built-in.
You can assign a value of the analog input to an unused Mach3 DRO register and use the same register as the duty cycle of the selected PWM output.