I think the videos are excellent as they are, pretty much. Making everything more slick and polished would definitely lose some of the appeal for me. The whole idea, after all, was to be like the original 'Channel 9' on the plane, where you get to hear everything
exactly as it is, not staged or approved, etc. If it went in the more professional direction, it would certainly seem more as if everything is being too controlled, which I assumed is exactly the impression you don't want to give.
As others have said, I just think you need to have an additional mic for the interviewer. I even like the sometimes shaky camera work - it just seems much more low-key, something that anyone might do, more real.