I'm building the trailer topper to use in the near-term as an enclosed cargo trailer, but I've designed it to be easily configured as a camper using the same basic parts, a few things I've already built plus a few new bolt-in parts.
One thing I've already done that will be part of the camper top is the pop-top, it's will be the roof of the topper:
Also I'll use what I call the "Trail Kitchen" that I designed and built earlier this year. It was initially designed to go in a Jeep, but it can just as easily install in a trailer. It's got a fridge, a lot of table space, a drawer and a water supply. This kitchen photo was taken a few weeks ago on a camping trip in Death Valley:
The kitchen installs to pretty much any flat surface, it's got a double extension slide and the tabletops fold down once it's slid out. It stores very compactly.
Doing a little photo-editing, the kitchen would look something like this in the trailer. The hatch above the kitchen would be configured as kitchen storage. I built the trailer with tailgates at both ends, so it's easy to have the kitchen slide out the front.
The camper would look something like this:
This x-ray view shows the sleeping platform above where the kitchen slides in and stows; also lots of additional storage below the sleeping platform. And lots of headroom with the pop-top up.
For now I'm focused on getting the basic topper done for cargo use, but once that's done the next phase will be the camper components.