I like the idea of using an RV shell. You could rip the plumbing and gear out of it and use it for the bus and then build bunks in the holes you made.
As for towing it, you will be very surprised how easy it is. I towed a 27' camper behind my 10 window dog nosed International. I've never had an easier time towing in my life. Like Lapeer said, it tracks right behind the bus. It even makes the ride smoother. The length makes switching lanes more of a chore, but thats about it. I took it on some two lane country roads and 1.5 lane roads in winding hills and never had a problem. I even backed it down the side of a grassy hill without incident. Get a backup camera and it will tell you the angle of the trailer if you cant see it in the mirrors.