There's at least one B+ that has a bed winch down from the ceiling, but at that point it's almost a small Class C, so I doubt it fits your needs.
The Winnebago... Travato (I think) comes in a floorplan with a very long wet-bath and a bed next to each other in the back of the van... I'd think that wouldn't be too hard to raise the pre-installed bed and put a 2nd bed beneath it... especially if a mattress-on-the-floor is acceptable.
Beyond that, I can't think of one... but it's been a couple years since I really dug into every available floorplan out there.
If you don't mind spending a bit of coin, a semi-custom shop like Advanced RV or Coach House RV should be able to build something to suit...