Agreed on the Slider...
Seen 'em in operation, and they'd be rather easily done, just make a screw-drive to push-pull the axle-assembly forward/aft, and then rails for the assembly to slide on.
The folder, that would seem to be more complicated, as you'd need the right angles on the neck to get it to bend right, and then there are the power-disconnect issues... but you have those for almost all the trailer lighting assemblies (no-one's made a 5th wheel-mounted power transfer system...)
Would love to see one of the these made: A Murray Robo-Link
http://www.youtube.com/watch?v=8u_IW8g9aN0
Why, you could hide the electrical links for the trailer lights in the link itself with leaf/pin-contacts, seeing as the 5th wheel stays connected.
Anyone else?