This is an exceptional and intriguing build, utilizing an off the shelf product and reworking it to one's own specifications!
The addition of fabricated structures and components to existing or reworked standard items opens up a realm of possibilities for camper construction and modification!
Whilst inspired by owner fabricated builds, I'd think that they have skills and equipment I don't have so I can't do those things!
Buying camper plans, but unable to aluminium fabricate or pay someone to, I finally decided to get myself some equipment and to learn how to use it!
At some point I'll work to a reasonably good standard to make things sufficient for my purposes.
I say this as I see posters saying they don't have the skills to build what they want, so perhaps think about actually learning how to do these things?
The Internet, websites, forums, podcasts, blogs/vlogs and YouTube are all free resources, as are libraries. Books are great too, and inexpensive pre-owned!
There are Engineering/Technology/Build Centres in many US cities where one can learn under guidance and hire tools, equipment and machinery to do a multitude of things (vacuum forming, 3D printing-including metal printing, machining, welding, fabrication, etc).
Instead of just thinking how great it would be to be able to make or adapt something, actually start by learning how to do it!