Thought about a pop top too, tempting & practical but does put a sizeable hole in the budget!
Going back to the Bongo, most of the older vans have a motorised pop roof. We kipped in ours when the van was loaded while touring in mainland Europe; with the roof up there was enough room to access the fridge, sink and hob in the van, and then with the roof floor down we’d climb up into the roof and lay down a thin mattress. It’s incredibly useful as it turns the van into a genuinely usable space for living in.
However it is just a glorified tent. It ain’t warm in winter. So, it depends on your specifications when you want to ‘sleep in a camper van’.