I get what you're saying but I'm not exactly sure I agree that 2 characters who engage each other physically can always be done separately. That said, in the ipisoft gallery there's a guy that did a video game and used ipisoft to act out (he says) 100s of assassination acts and death acts and then stitches them together. In a live performance of both at the same time, I think you're going to get a different chemistry. Two dancers for example. I do think that I'm going to want two actors at once because without the real-time interaction, cleanup will be nightmarishLy difficult.
Dual Kinect is the only way I'll do anything. I've tried with one and there's gonna be lost information for tracking if I don't see front and back side of my actor...and they will be turning around. Here's a sample I tested in my company hallway:
https://youtu.be/lWnIzdR_9RA