There is always the "stealth climber" van.
The better thing you can do (IMHO) is buy diesel and run it biofuel and heated veggie oil. And get the 6.0 Diesel because that's what I have and I need someone to pioneer this for me.
I would think there are a host of other things, considering you're probably going to be building your own- there was some discussion of composting toilets awhile back. You can use it as a vegetarian/vegan lifestyle vehicle. And add some solar panels and go off the grid.
Speaking of building the interior yourself, which I think is probably necessary to get all wood, you're probably going to have a much smaller eco-footprint by doing everything but the pop-top yourself, even if you employed the same materials SMB would.
Meanwhile I'll get the bumperstickers ready:
SMB: Eco-friendly since 2010