I like the Q5. It should make a great TV for a small Airstream. I would be more concerned with the exceeding the max rear axle weight rating and the GVWR than the tow rating.
Give Andy T. a call. Whatever he says, I would go with it. He is a towing expert.
You might look for a vintage Caravel
or Globetrotter. It would tow either of those with ease. There would not be much difference in the function between a quality restored Airstream and a new one, but you would save a pile of money and also not have to deal with depreciation if you decided to get something bigger, along with a larger TV.