I think a lot of van builders install "permanent" walls or other things that cause problems in the future. I'm interested in starting a thread about the importance of building vans in a way so they can be repaired. I'd like to hear examples from people who created easy access to fix their van or be willing to share examples of when you did something more permanent in the van build and then had to work extra hard to fix the problem.
I'm just finishing my first build out of a 2019 Promaster high roof extended van. Threads like these have been very valuable. I've made extensive use of extruded aluminum (EA) and have only drilled/cut holes for the Maxxair fans, sliding door window, roof top wiring (solar, lights, weboost) and 1 1/2 hole for composting toilet ventilation. Other than these, I've made use of existing holes. I used screws, plus nuts and t nuts. As such, everything is "reversible" and repairable (insulation and sound deading was glued so being completely "reversible" would be difficult). Obviously, some easier than others.
Given my first build, it allowed for correction, and from a potential accident/repair perspective if I needed to fix something, it would be possible. Not to mention the material strength, and subsequent safety, is the best. Repairing the wiring that is routed in the roof chase(s) would be the most difficult, but I did add additional spares as a preventative measure. Not the cheapest route, but very happy I went with this.