I think the gadget is too small, for one thing, it would necessitate a very close lens to subject distance.
Secondly, the interrotron's unique effect works IMO because the guest has nothing but your disembodied head to focus on. This gimmick you're looking at keeps the interrogator right there at the camera, you can see the guy standing right there. I just don't think that can ever work as well. Because they will keep straying with their eyes to try and pick up body language cues from the exposed parts of the body they CAN see. It's reflexive and natural and I don't think you can stop them from doing it. The whole thing is going to be very distracting to persons experiencing it for the first time.
IF you still go with this gizmo, I recommend you put yourself and the rest of the rig behind some black pipe and drape as a camera blind, with only the final mirror/lens assembly poking out.
This definitely looks like a try-before-you-buy investment.
I don't think it would work very well, for one reason: the cameraperson/interviewer has to be almost superhuman to keep the interviewee focussed on him or her. With the "interrotron," any discordance in the relationship between interviewer and interviewee is much more obvious. It is much more disconcerting to see someone look away, when their main eyeline is to camera. When someone is already looking off-camera, that break isn't nearly as obvious or dramatic.