I thought it might be a case of overblown bureaucrat ego, too. I am
going to pass all your great ideas on to the new owner. He is a
forester, so he should be handy with tools to make some new VIN plates
(I wondered why he just didn't do that in the first place). If not,
he can always declare it a homemade trailer. There's plenty of ways
to get around the "system" - you just have to have a little
imagination (and paranoia).

Thanks for all your help!