Hi Fred,
The reverse needs two wires as you describe. (Blue and Black) Just need to ground (Blue)reverse wire. But the PAS needs three, 5vdc (Red), ground (Black), and the (yellow) sensor wire. So combining the 5vdc and sensor wire as you suggest would not work. I can see how the plus symbols on the diagram could lead one a stray.
I think it could still be done with a three way switch though if you had batt ground to the center pole. Blue wire to the top for reverse, and PAS
ground to the bottom pole to enable PAS. Thereby switching the ground...Switch up reverse, middle off, switch down PAS...
And welcome to the forum!
Regards,
T.C.