The problem is always the spare tire. We incorporated it into the camper, but it takes up a lot of valuable storage space under the double bed.
With a cab over, even a custom build with an extended floorplan with departure angle, you would need to retain your floorplan for kitchen, dinette and toilet. We use an Evershower which stores under the toilet. Your water capacity depends on how you will use your truck. For boondocking for a week, for two, you need 50 gallons, plus you need 10 gallons for grey water. An overcab poptop with north-south bed and storage down one side of the bed would be ideal.
We avoided the "classic yacht" interior look and stuck with white, either gelcoat or 2 pack paint. The primary reason is ability to clean. If you've ever picked up some Aussie red dust you will know all about that.
One other thing to consider is the strength of build. Your Unimog will go anywhere, will the camper? We built very strong walls, bump rails and poptop mechanism. I've already tested the bump rails once while driving through a forest. It was user error, but hitting the top front edge of the roof could have been catastrophic, but for the quality of the build. If you are just hopping between RV parks then ignore all of the above. Pretty well any commercially available product will do the job and for a lot less money than custom.
