The Schienenzeppelin would by far be the easiest. Simply downscale an existing Zeppelin model, and add trucks in cut-outs fore and aft. The actual vehicle had been built as a project by the Zeppelin works, although some sources say the Z-Werks contributed as design consultants only. Either way, the vehicle is supposed to have reached 115mph (say 185 kph) on at least one occasion, though it had reportedly been designed for 85 to 90 mph (say 112 to 120 kph).
What I recall most is that the vehicle was so good the authorities became scared of its' success and banned it on the usual "unsafe" excuse, though no safety faults had been found, save a very slight instability in high-speed curves.
All of the was in the original Maerklin N-gauge (1:160) handbook I read for the model engine, then valued at about NZ$485, in about 1979. (I admit I am open to correction on some of the details I have given here.)
The other vehicles you show are equally interesting, though the Russian jet-job would make a fine partner to it's American jet-job rival, with the French jet-job rounding out a trio.
I do hope someone takes these up as designs, even if as long-term project.
So far as I know, the Maerklin Z-gauge Schienenzeppelin was the only model example of the vehicle to be produced, and even then in reasonably limited quantities.
Kind and Respectful Regards Armorman my friend, Uyraell.