It is quick to switch backs and I agree with all you said about a slide for every back and the slide on the Polaroid being different. It will be a heavy setup but the MF shots will yield priceless prints to be treasured.

I still have an old Pro back without interlocks along with some Pro-S backs so I always have to be careful to know what I'm using.

The Polaroid coverage makes me wish for an RB69 instead of an RB67 though.