For Jeff's question about strutural integrity with only an exterior plywood skin, I emailed him this answer but want to post it here for others to see and comment on.
As for my opinion, I believe that the framed up sides, ends, and top, with large skin pieces of plywood attached, all assembled, provide all of the structural integrity that is needed. With the cabin attached to the frame, you have a rather solid "box" that doesn't really need the interior skin to help improve it's stability. I'm not an engineer, but have observed the strength of a simple cardboard box in resisting being warped or twisted when it is fully enclosed (top, bottom, sides taped shut). You can bend or twist a single piece of the cardboard, but not the assembled box...try it.
I think the appearance of the interior skins, as you describe it, would be pleasing to the eye as well. Being able to remove a single piece to get to something in the wall or ceiling would be an advantage that I hadn't considered. Good thinking.