4WD Westy Sprinter!!
Christian,
You've discovered my dream too. I have a "NAFTA James Cook", as they are sometimes referred to here in the US. They were imported by Airstream, not Winnebago. I have mulled over converting mine to 4WD, now that John at Upscale Auto has a kit for doing so. Not cheap at all, but the resulting vehicle would be unique, to say the least...
When Airstream imported them, they did a few things that I would have to undo, such as the underside propane tank, and maybe the generator that was installed in place of the spare. And maybe get rid of the rooftop AC, which is not normally found on a European James Cook.
But the basics are there; the Westy Sprinter layout is arguably the most functional layout of 18 feet that one can get. So much so that Westfalia still uses it, in their Sven Hedin camper. After 4 years of ownership, I've yet to see how they could really do any better.
Keep up the search!!