Here is a top pick in the UK for a "B" van:
The three notable things:
First, the sliding door was replaced by a RV style door. The disadvantage is that this utterly kills any stealth aspect whatsoever. However, the advantages are the fact that there is no sliding/slamming noise every time one wants to go in or out. It also provides better insulation.
Second, the slide-out. Since this is a UK van, the slide is on the starboard side of the van.
Finally, the van platform. Just a plain old Ducato.
This would be a great floorplan in the US, but again, European floorplans are hard to translate to the US due to the differences in plumbing and the need for a generator and A/C.