As I was trying to say above, when I disconnect the smallest connector, the only one that clips in as it as a right angle to the front, that one controls motors on mine.
Taking the gimbal off and on is a *****. The two connectors in the front pull out easy and it is difficult to get the dampining balls in when you have the plastic pin in the hole (the back one is tough). but the one little connector that I am refering to above is the one that breaks if you crash because it is clipped in, but that also works to our advantage as it is the only one I an get off and back on without dropping the gimbal dampining plate to access the two front cables.
I have not tested this for this purpose but if that cable is not connected I am unable to pitch the camera. It might still be trying to hold an axis level, and this would need to be determined so motors do work out. The middle connector, the biggest one, powers the unit at a minimun. If it is not plugged in nothing works. the one on the right (as you face the unit) that one is still a mystery to me..probably a bunch of techies do have a complete run down on this, but there is a value to this knowledge at this point. good luck, what you want to do is possible.