New "B" Sprinters can pull 5000-6500 pounds. The ProMasters, 3500 pounds. No clue on the Fords. The older vans, easily more than that.
As an alternative to a small TT, one can always have a custom enclosed cargo trailer made. The back would drop down, but have a RV style side door (so it can be opened from the inside.) Then, toss a 12 volt battery, ceiling fan and a side window, and it would be usable for more sleeping space. I've even seen fold-out bunk/shelves. Of course, this won't have the amenities of a travel trailer, but it does get one out of the elements and off the ground.