This is something I have been thinking about. Unfortunately, you are going to have clearance issues from the bulkhead immediately behind the seats (of course you could cut it out).
The only Class C that I am aware of that have swivel seats are the Coachmen and some Forest River models. If you look at their bulkheads, they are far smaller than typical.
Perhaps though, you can get them to work. I would not mind if I had to move the seat position and seat-back forward/backwards as you rotate it. Not as convenient I suppose as simply swiveling the seat, but the slight difficulty in rotating the seat (if it can be done) would be outweighed by the convenience.
Even if the passenger seat were the only one to swivel...
Atwood makes the swivel mechanism for Coachme/Forest River. I have been in contact with them, and obtained a drawing so I could see if they would be worthwhile trying. But they were far more than $200, so I kind of dropped the idea.
The only thing that works on a RV is the owner...