..I must preface this by saying I have no specific experience with flat towing a mini cooper, can only speak from what I've heard from various places. Could be totally wrong, but...
The fact that its a manual tranny, means towing it 4 down may well be possible, without hurting the drivetrain. Many manual tranny vehicles can be towed that way.
However, IIRC the challenge with the Cooper Minis is in finding a way to attach a tow bar to the front of them. Not that many base plates available for them, as many Cooper Minis don't have anything solid enough in the front to attach a base plate to.
Before buying the Cooper, contact Blue Ox (or maybe Demco and/or Roadmaster), see if they make a base plate for it. If not, I would ask the guy who said he tows a Cooper Mini, where he got his base plates, or how he attaches a tow bar to the front? Maybe he knows of someone that custom fabricated him some base plates?
(..Maybe someone that owns a Cooper Mini will chime in, and correct me if I have mis-spoken?)
Will and Cheryl
2021 Newmar Baystar 3014 on F53 (7.3 V8) Chassis ("Brook")
2018 Jeep Wrangler JK ("Wilbur")