While I imagine this is doable (nearly anything is doable with sufficient time and money), I think the extension has the potential to be a problem in the future.
Basically, your rear wheels are a fulcrum when turning, and your tail swings farther than you expect. If you extend the body too far, you run the risk of the tail swinging into another lane and causing damage.
I have not seen where anyone has done this, and perhaps a modest extension would have minimal impact. There's a user on here that has recently removed something like 3 window sections from their bus to shorten it, and if you two aren't too far apart, that might make a donor shell for you to work with. Extending the frame can be done by sistering in a smaller frame rail within the existing one, and clamping it all together. There are frame shops out there that extend frames and would be able to help you as well. On the other hand, if you're only talking 3-10 feet or so, you can probably do it yourself.
I'm curious to see how this goes.