Is the Power Level setting in G2 not of any use with the DUE? I figure that this is working only internally in the electronics of the Tinyg board.
G2 Power level uses D/A converters to set a voltage, fed to stepper drivers to replace the typically static voltage set by the potentiometer.
You could hack the driver devices (depends on design), but you will then find there are not enough D/As or pins to implement full 6 axis unique control.
My drivers have siwtches to set the power … anyway it was just to clarify things up a bit.