Not that the E-series is being phased out, but if it were, the T-series could be manufactured in any size needed.
Just as with the unibody Sprinter, to make a cab-chassis from a Transit, it is necessary to build a frame and mount the cab of the unibody truck on that frame. Size and capacity of the resulting chassis is simply a marketing decision.
I don't see the market for US-style C's, 24 to 30+ feet and 14,000+ GVWRs, lasting much longer, if anyone here starts producing Euro-style motorhomes, under 7000 pounds at seven meters length, capable of 20-30 MPG. That could take a while to happen, we are historically slow to accept smaller anything. Winnebago has made at least four tries at the smaller motorhome concept, producing something similar in size and equipment to contemporary European RVs, and they've been not well accepted here.
The ProMaster will be the first chassis offering suitable to this type of motorhome, but the one we are getting can be about 50% 'bigger' than a global market Ducato, Master, or front-drive Transit. Not even Ford thinks we are ready for the 3500 KG van.
So to begin with, I suspect the first ProMaster Cs will be about as big as they can be on the highest GVWR ProMaster chassis offered. First models will likely use our current house construction techniques, and include heavy features like slideout rooms, gensets, air conditioners and wastewater tanks, because that's what we are buying.
FWD and small engines work in Europe because the motorhomes on those chassis aren't any heavier, and not much taller or wider, than our full-size SUVs. About 30% larger than our minivans.
