That's some insane Heath Robinson stuff. Love it heh...
Somewhere last year (can't remember where - sorry) I saw some article about an articulated Brompy where someone had made a custom frame part that clamped to the seatpost of the front bike and then replaced the headtube of a second brompy at the hinge so that you had a three wheel articuated tandem - kinda like a towed kids trainer but all the same size and rather elegant. Very cool it was too.