When you say shuttle bus, I envision something the rental car places use at airports, not a full size 45' bus.
I is an idea that has always facinated me as well. The shell is certainly far stronger than any class C having to stand up to tougher safety standards I imagine than any RV.
Sounds like a great project for somebody with the skills, the time & the place to make it happen.
Just understand going in that nowhere near whatever is put into it will be recovered when it is time to sell. Same as a custom or heavily modified boat.