@devlord There is a very small Airstream, made of fibreglass instead of steel -- Bantam? Forget the name now. Possibly not made anymore. I know I considered it for use with a Wrangler. I've heard very different numbers for MINI's towing capacity, from zero to a tonne; I'd ask a dealer, directly. And if you do it, have the dealer put the tow package in, not some sketchy after-market job.
There used to be trailers made for Bugs, so I'm sure it's possible.
@devlord Bambi.
https://www.airstream.com/travel-trailers/bambi/
4.9-6.7 m long, 2.44 m wide, 2.88 m tall (w/ AC); single axle; GVWR = 1.588t
So, not for all vehicles, unfortunately. And not for MINI. The tongue weight alone is probably a deal-breaker.
But plenty of other trailers are light enough.