The 2012 BAE is probably Rodney's who detailed his intent to build the truck into an RV for him and family on Expedition Portal, but the threads have now been deleted. If it is the same one, the vehicle seems more than road worthy and can be made ready (IMO), with all the work that he had done to it --- just unfortunate the batteries weren't taken care of. GXV will take care of you, or knows someone who can take care of you to make sure the vehicle is in tip-top shape and expedition worthy. Here's the
history of the vehicle in PDF that is still active.
If it is the same truck, I'd be surprised if a pass-through is going to be possible, but that might not be important to you.
You might check out
Expedition Portal and the the Kenworth K370 chassis that GXV has been using lately. A few of those have rolled off the custom manu line there, and owners are now driving them around. I mean if you're going to spend the money, I don't see a big difference in capability.
But before anything else, I would give
Andreas in Las Vegas and Box Manufakur a call to discuss, and the other
Andreas at Total Composites to discuss your habitat ideas. Having either one of these companies build-out the box, sub-frame, and design is going to be way cheaper than a GXV, and they have the European styling, design, and experience under their belt.
Good luck with the build.