I'm planning to live full time in a large DIY truck camper on the back of the Cybertruck, made of stainless steel and covered top and sides with solar panels. Truck campers don't seem to be on your list for some reason?
Have you see the shape of the cybertruck? Good luck building anything that will fit and be functional.
Where will you weld/bolt the frame tie downs? These have to go on the frame. How will the turnbuckles go around the angled bedsides?
The cabover won't fit on the roof line and the bed floor is to short for anything livable.
The CG will be awful. Conventional trucks have the powertrain up front and you can pretty much put the arrow in the middle on the rear axle. With a 50/50 bias this is impossible once you figure out that you will need at least 24 inches of rear overhang for the plumbing and shower etc. Don't forget all TC's are basement designs and this will push the floor you walk on up by at least 12-14 inches. Maybe more.
The best you might come up with is a vertical stainless box. Who would want to live in that?
Don't get me wrong I love the idea and I just bought a new AF 990 TC as off the grid truck camping is awesome. But the vehicle you are choosing is probably the worst for the task. My "smallish" 990 weighs 5300 lb with water on board.
If Tesla wants to build a truck that could haul a TC it would not be that hard. Flat conventional bed/bedsides and moving the battery forward somehow would do it. And a roofline that can accept any TC including a homebuilt. You want 3-4 inches clearance max with the cabover or you will be dragging a lot of air. And dual rear wheels make the rig stable at all speeds. Tesla would need to add some kind of "frame" to bolt or weld the frame tie downs. The load on these points can be considerable under normal use and extreme in an accident. You don't want the TC and truck parting ways.
The Ford branded campers from a few years ago are built completely of aluminium. Even the cupboards. The company making them is no more but they were really neat rigs. Light and functional. I think they weighed out at about 3800 lbs dry.