I guess I’m kind of a non conformist, but I’ve studied camper vans of all ages extensively, and converted & restored everything from vans to buses, and have been living on wheels for over 50 years now…
I will NEVER strip a van or bus with factory floor/walls/ceiling unless there are telltale signs that it’s absolutely necesary. Things like a soft floor, obvious leaks, or water damage. Even then, I only repair what’s necessary, and try to restore it to original.
I know from experience that no amount of insulation will keep you comfortable, only active heating, cooling, and ventilation will do that, and it will work with or without added insulation. I’ve done winters down to -60°F to +120°F comfortably with no added insulation, and no window coverings in rigs with many many windows. To make a long story short, a campfire can keep you warm outdoors with no walls or ceiling, staying warm/cool in an enclosure is much easier.
I just remove the rear seats as desired, keeping the floor/walls/ceiling intact whenever possible. Even if they’re not perfect, much will be hidden by cabinets, bed, etc, and hidden places don’t need to be perfect. Actually, nothing needs to be perfect. It will get worn & damaged with use anyway, that’s called character.
I put my time & energy into comfort, convenience, & reliability. I don’t fix things that aren’t broken, or create unnecessary work for myself or others.
I have an ozone generator that I will use on a new to me rig, or sketchy motel rooms, to kill off any bugs, mold, mildew, smells, etc. They also have ozone bombs, like bug bombs, if you don’t have an ozone generator. They’re available at places like Home Depot, you can google “ozone bomb”. Some might be called bug & odor eliminator. They work well.
"Practical beats popular every time." ~ Truth Matters