Being a Motorhome owner and a T6 owner, and having a business in the Caravan and Motorhome industry, I never really understood why the later VW platform is not used on general Motorhome builds anymore. It's not price, because the Mercedes platform is a common upgrade from the Fiat Ducato, which is the most common base for all manufactures, including my A-Class.
The T6 would of made a great Motorhome, and the option to go 4motion, DSG or Manual, all the different power outputs, and all the different spec levels, in comparison with a Fiat Ducato, which has an awful auto box, 3 power outputs, but the biggest being the only one actually good enough for some of the huge Motorhomes, and not a huge amount of upgradable spec, unless you opt for a Mercedes, which puts a huge amount of cost on top of your base vehicle.
The VW option would of given a much wider upgrade option list, that would of added to the initial purchase, but knowing my industry and my customers, I think many would be happy to pay for.
Maybe the VW dealer network isn't set-up to deal with some of the huge Motorhomes like the Fiat and Mercedes commercial side is. Or maybe VW in general just didn't want to supply the base vehicles for conversion when they have things like the California. What ever the reason it's a shame, because some of the old Karmann stuff was really nice.
As for the above, it's nice but a very limited market in my opinion. Although knowing what
@Loz and some of his friends have done over the last couple of years, I can think of a couple of people that would be interested in one of these.