Bed space takes a back seat for the above reasons. Trailer rentals are available if absolutely required.
A 4' bed is still 4' better than a Bronco has.
Will a Bronco fit three car seats across the rear?
Easier to find a Bronco with IDI or easier to drop a CC on a RC chassis?
I was referring to the Centurion conversions that were offered for sale in the late '80's and throughout the '90's, which was basically a crew-cab truck with a Bronco rear end instead of a pickup bed. Something like
this. It's more like an Excursion than a 1/2 ton Bronco, and would give you three rows of seats and the ability to fold the rear-most seat down for extra cargo area when needed (and, with that seat down, I think you'd actually have more than 4 feet of cargo area). And, with the enclosed roof, it would be easier to stack more small items (boxes, suitcases, etc) without having to worry about them falling out. I imagine it would be easier to put car seats in that than it would in a traditional crew cab, although I can't say that I know for sure.
With all that said, unless your friend has the time and ability to fabricate a shorter bed and deal with the cab mounts to get a crew-cab cab to mount on a regular-cab chassis (which can't be an easy thing) or the $$ to buy a one-off project like the one listed, IMHO his best bet would be a conventional crew-cab truck or, if he went the PSD route, an Excursion. Another thought would be an E-series van...in fact, based on what you said he needs, the van may well be the best way to go. A van would be a lot more family-friendly, and could tow the same trailer that a truck could. IDI vans are not quite as common as trucks, but they're certainly around. I wish I could have kept my old 6.9l E-350
I'm sorry if I sounded confrontational earlier; it was not my intent...I'm just stating my opinion...