I've not researched this, but I believe that the Accessory Wire on the Hardwire Kit merely senses if there is 12V present, and uses this to switch in and out of Parking Mode. I really doesn't draw any significant current from the Accessory Wire.
What if the 12V Battery Wire were connected to the Power Magic Pro, and the Accessory Wire were connected to a 12V source that is only present when the ignition is on.
In this case, I believe that the F750 would enter the Parking Mode using the Power Magic Pro as the source of power when the ignition is turned off.
Basically , the best of both worlds.
RodeoGeorge