SuperTrooper -
This sounds similar to these threads :
http://ecomodder.com/forum/showthrea...ailer-201.html
http://ecomodder.com/forum/showthrea...idea-4420.html
The difference is, I think you are seeking greater *design integration*, as seen in the shuttlecraft option.
I think it's hard to translate the shuttlecraft to an auto because boat layouts "push by design" (engine and steering aft).
However, with the advent of a lot of "drive by wire", I think you could have two vehicles connect to each other pretty seamlessly. For instance, let's say the "pusher" is a RWD Pontiac Solstice (fun!). When you needed to have a bigger vehicle, it would be attached to the rear of the "pushee". Maybe it's front drive wheels would be elevated off the ground or have a high quality "lock straight" mechanism.
Here's an example that doesn't raise up the Solstice's front wheels :
Overlap Test Image to line up tires :
Solstice Mule "inside" Vibe "pushee" :
In the above picture, the Vibe would have no engine. It would just be a shallow trunk and the steering mechanism.
CarloSW2