They actually made a pop-top Caravan. I believe it was a Get-A-Way van conversion, but it worked just like a Westfalia. The ones I have seen have all been early '90s models, but they may have made them after the bodystyle change in '96. If you just want a 2 seater camper, check out how these guys convert their Astro vans. Click on the More Info link on this page and scroll through, you'll see how they lay them out inside.
2-Seater Campervan
Its a simple conversion they way they do it, lots of storage, and it's all done with plywood and some foam and fabric. I know these guys (sell them most of the vans the have), and it's a pretty simple but effective way to do a cheapo RV. They sell out of rentals every year (130 vans at their office here), so they must be onto something with the layout being decent.
