Interesting; I can agree with a lot here, from diferent members, parts or completely
Just as info, I would like to add the following, feel free to add or correct yourself.
Westfalia had a very difficult financial time at the end of the last century and, although they had the nugget on a ford transit basis but no further interfaces with ford, a collaboration between them and vw was possible. Maybe VW wasn't interested and/or couldn't pay for westfalia because it was acquired by Daimler/Chrysler in 2001 who had already the Marco Polo there since 1997.
Mercedes naturally wanted to put 'their' Marco Polo in first place... and the California, which was based on a Volkswagen was at its end because a new transporter would come (T5). They didn't want to put a cent more into the development of the successor to the T4 California and the collaboration between Westfalia/Mercedes and VW came at its end. VW itself developed further on and that's how the T5 california came. The rest is history as we know it, with the good and the lesser sides of the product.
Btw: VW already 'helped developing' the T3 california (1990) and although it kept the name westfalia, volkswagen saw it more as a product of its own. This is how they got the name 'california' and took it with them when the california camper (T4) discontinued at Westfalia. The T3 California was a simple, cheaper version of the Joker, Club Joker and Atlantic. This was mainly to stimulate sales.
Some more titbits: westfalia worked closely together with vw: of course the campers which were sold at vw dealerships with the warranty included, Westfalia also made designs and models (also 1:1) for vw of the successors to the t1 and even more (and Daimler/Chrysler wasn't fond of that close companionship Westfalia/volkswagen).
There is also a westfalia based on fiat: the Michelangelo. An exercise with two separate seats instead of a bench and a nice little camper but a flop in sales. They are as rare as a hen's teeth.
Westfalia had another hard time with selling their museum pieces as a hopeless rescue plan and low point in 2009. This didn't help and Mercedes got rid of Westfalia and it became a brand of the French rapido group in 2010; only the Marco Polo is still made in Germany.
We ourselves were interested in a westfalia product, the kepler six or its sister model Melbourne from Stylevan (same as a westfalia and made in the same factory). We looked at this extensively and decided to buy a t6.1 california coast for our own reasons. The handy finds of Volkswagen that others don't have were just a few of them to choose a cali when we were looking for a successor to our old faithful westfalia t4 california.
I hope this was not too much reading