The one I saw looked very cool very high quality. I don't really remember the details but I guess I did remember the colo in the name. One thing I would do is maximize all the space. While a non uniform bump would look wierd, using the rest of the space for a good roof rack, luggage rack, solar panel would make the van look better and be more useful.
Except for standup height, I don't see any true need for a full length popup. The bed is usually two layer or maybe 3. You can stack them or flip one down, so when you pop up the roof a large part of the area will be stand up height. When you want to go upstairs to sleep you rearrange the bed to be full length, and climb up. On my VW van I used the fridge as a stepping stool. At 20 it was easy at 50 it would be harder. I would design the cabinets below to make climbing up as easy as possible to avoid needing an extra ladder.