Take a look at "the bayfield bunch" blog. Al and Kelly did a real nice job of redecorating a nice, fairly new motorhome with a southwestern flair. Lots of bright native colors and décor. IIRC, they had negotiated a trade in price, without bring the thing to the dealer. When they arrived, the dealer simply refused to accept the rig for any amount. No deal. In the O.Ps case, it's a matter of not only greatly damaging resale value, but creating the possibility that the rig will not only sell for far less, but be extremely difficult to dump at all.
We bought our used class A in Fl. at the end of the snowbird season. You couldn't swing a cat down there, at that time, without smacking a motorhome for sale. We literally looked at hundreds, as some dealers would have dozens to a hundred or more, on the lot. I quickly learned that if I stuck my head in the door, and it was obviously "customized" it was time to turn around. Why? Well to put it charitably, it is a red flag. Many, but not all, folks that have the mindset to rip, tear, and redecorate, are not quite the craftsmen they fancy themselves to be. It was pretty common to see really sketchy workmanship, and odd, sometimes bizarre "improvements". The next jump in logic for me is, "If this is the kind of owner who takes a paint brush to beautiful hardwoods, and creates a really off the wall interior, what else did he think he was good at. maintenance, roof repair, engine upgrades?
No, I think that whole scene is best avoided. Don't do it, don't buy one from somebody who thought they could.