Okay, an update on this.
First off, I did get a Ford Transit Connect, Long Wheelbase version. These are available in long wheel base and short wheel base, the short wheel base isn't much help over a lot of other vehicles. The long wheel base is fairly common and roomy. The Dodge Ram vehicle seems to have similar interior dimensions to the LWB version, by the way.
Got it home, and had to run the tandem out to see how it fits.
Straight in, it won't fit easily.
Turning the front wheel sideways, the tandem is several inches shorter, and it will fit going straight it, with the rear wheel between the two seats. Here it is, with my wife holding it in place for the pictures.
The driver's seat is all the way back, the passenger seat is not, but it looks like in that position, it would ride fine and wouldn't intrude on my personal space at all.
Alternatively, it can go in corner-to-corner. Doing it this way, you still have to turn the front wheel. Obviously, it may depend on exactly how the seats are adjusted with this option.
With the bike in straight, if you run it in between the two seats, what hits first, on my bike, is that the derailleur cable is going to hit the armrest. So to extend it farther in, it's got to come up slightly. That would be okay, there's plenty of "up" space available, still.
For reference, this is a CoMotion Primera about 3 years old, in "Large" frame size, with 700 wheels and 32mm tires. The handlebars are Woodchippers that are fairly wide. No fenders as you can see. I'm about 6'-1", so saddles are reasonably high, but no problem on the height.
There are six tie downs on the floor. I need to make wheel holders that holds the wheels in place and a strut that attaches to the saddle to keep it upright. It seems to me that the straight-ahead position would be handier for use, and the diagonal position would be easier to make the tiedowns work. But I'll give that some thought and see what I come up with. It'll be a week and a half before I need to haul the tandem anywhere.
Oh, I said the Dodge Ram version was similar dimensions- it is, but also, the gap between the seats is smaller, so beware if you try to run it in that way. With either setup, you don't have much extra room, so a few inches difference in bike or vehicle dimensions will make a big difference in how this works.
If you look at dimensions for the vehicles, the rear doors extend several inches into the floor area and the rear seats hang several inches back in the floor area, so that makes it hard to use the floor dimensions they give.
Some comments on the vehicle itself, based on the first 100 miles-
These are sold as cargo vans. A lot of them don't have any windows in the rear part, some have only windows in the rear doors. That doesn't affect bike hauling, in face, fewer windows is more security for bike hauling, but does affect visibility. The windows on each side and back are uncommon, but that helps visibility a lot, which is why I picked this.
The rear interior is unfinished. On mine, the doors have fiberboard panels inside, and I expect that adding windows simply involved switching out doors. There are some panels on the sides, other areas where it was obviously intended to be covered with something else. On the Dodge versions, all the "windows" are either glass or steel panels that have been inserted, it's not that they don't cut the hole, they cut the hole regardless and either plug it with glass or steel panel. On the Fords, the door "windows" are like that.
They do sell passenger versions of these, usually slightly higher, and I would have bought one of those if things worked out right, but this worked out a little better.
These are intended as commercial vehicles. At a couple of the dealers I went to, that meant I wound up dealing with their "Fleet" manager and salesmen. They're wanting to sell a dozen F450's to people, these little things are absolutely the cheapest thing the Fleet Department handles, and for just one of them, they wouldn't even bother to call me back. But, at the dealership I went to, there wasn't any "Fleet" division, they were real nice and all worked out well. Just to plug 'em, that was Mac Haik Ford in Desoto, south of Dallas.
Mine is the plain-Jane no-option version. It still has automatic transmission, power windows and locks, and radio, but omits other extras. All the ones I've seen were 2015 models, but I assume the 2016 versions will be out before long.
Engine is real quiet, there is quite a bit of road noise coming from the rear, though. Ride is kind of trucky, interior is typical low-end new car. If you've driven a bunch of junky old vehicles in your day, this will all seem just grand. If you're accustomed to a plush Cadillac ride and handling or to high-dollar pickups, then maybe not.
These vehicles are basically the front end of a small car with a van built on, front-wheel drive, good gas mileage. The vehicle is minivan height, but the seats are low, so I've got like a foot of headroom in it. I could wear a top hat while I drove if I wanted to. Lots of leg room up front, seems bigger on the inside than on the outside, kinda like the Tardis.
Due to an odd tariff situation, these are actually imported from Europe as "Passenger" vehicles, then the passenger stuff is removed prior to shipping to the dealers.
I've never paid attention to these, but after looking at them more, I'm seeing lots of them on the road, mainly for commercial use. Nissan and Dodge make their own versions, both of which use Nissan's CVT transmission. I couldn't find much positive about that, so I avoided them. Mercedes makes the Sprinter van, similar, maybe a bit beefier, also pricier, also sold as Freightliner, and previously sold as Ram, I think.
These are cheaper than any pickup Ford makes. I think the Tacoma pickups would be similar pricing, and Nissan Frontiers a little cheaper, and those were my other options.
I'll try to update this when I get my hauling system finalized.