I'm not sure how a certification scheme would work, but open minded about it?

Something needs to change, else campervans will just continue being banned from more and more places where banning and/or barriers is the easiest and cheapest option for the local authorities in a specific area to deal with anti-social behaviour. Because that's basically what it is.
It's already been happening for some time now (since the pandemic et al) and will only continue getting worse over time. When people regularly behave like inconsiderate, selfish twonks, then banning and/or regulation/legislation will inevitably follow at some point down the line.