Load capacity is only 360kg, and that includes the passenger and driver. Caunting 75kg each there’s only 210 kg. left for the camper+stuff. Fuel capacity is only like 20 litres.
Mini’s don’t have a comfortable suspension system (they’re hard) but they don’t lower that much under weight plus my pick-up is pretty high on its wheels. I’ll do some testing with heavy load to see what it does under pressure. The engine is a +- 42 bhp 1100cc engine at the moment, but if that won’t do the job, a 2nd hand 1300cc engine with 60+ bhp could do the job and wouldn’t be that expensive.
As for the trailer/caravan, that is not an option, as they are very commun in the mini-scéne and I'm really going for the camper idea, just to be different

. Being in the posession of a pick-up, a camper is just THE way the job should be done in my eyes.
The tailgate folds down, not 90° but only like 80°, you can see that on the picture. But even then it’s still too short to lay down on an too narrow for 2 people, as the tailgate is only like 1.02 cm wide if I'm not mistaking, the space betwe the shock absorbers is even smaller.
