Plenty of examples of folks using Porsche Cayenne, BMW M5, Mercedes 350, VW Touareg, etc over on
Airstream Trailer & Motorhome Owners Community See all threads by
JFScheck for recent experience with Euro TD's.
Here's a big dollar rig: a 30' A/S pulled by an ML320.
Still others using VW Jetta, etc. Still more using Cadillac sedans, Honda minivans, Jaguars, etc. A truck is hardly necessary (unless desired).
Here is a
thread on the Eurovan as a TV.
Weight is not your concern when it comes to towing. If I can pull a 34' travel trailer and am still below some others at 16-mpg with similar 28-34' TT's weighing from 8k to 11k, it's about
aerodynamic resistance being the determining factor.
As those little boxes in your link above are as non-aero a TT as I've ever seen then its' other virtues had best be quite high. White pine framing and corrugated aluminum is about as cheap a trailer construction method as there can be.
Length of service is a real concern.
For $20k there is a big number of aero aluminum TT's that can meet the goals espoused in re 50k miles through retirement. My folks bought their TT new and used it 27-years spending next to nothing on it for repairs. The gulf between aluminum trailers and conventional white boxes is wide and deep.
Used is fairly meaningless as a term.
Unless already in process I highly recommend looking around more. Ask here or PM me or others, I know I'd be happy to help hunt down some examples (discussion threads) of suitable TT's.
Finally,
here is a thread asking about higher mpg tow vehicles for Airstream.