"BrewdogMN".....I'm an ardent supporter of the proportional air braking systems like the SMI Air Force One and the M&G unit, especially for towing heavy toads. But.....when it comes to towing something like a Mini with a large powerful motor home that has an engine brake, the Air Force One and M&G can be overkill. As a matter of fact, the only reason you need a braking system with the combination you have, is to be legal (braking system required on most toads).
With all that said, I would go with the NSA Ready Brake system. The brake is built into the tow bar. The whole system, tow bar and braking system, is HALF the price of any other braking system and tow bar. It's very effective and very simple to use. The installation is done on the car, (attaching a cable) with nothing to install on the coach.
If you do a search for NSA Ready Brake/Brute, you'll find nothing but happy campers. Here is a link to the product. Ready Brake Ready Brute Elite Tow Bar - By N.S.A. | HitchSource.com
The SMI Air Force One is a reasonably simple installation on your car, but I think you might be uncomfortable with the coach installation. It requires crawling under the center of the coach and cutting airlines, then running an airline to the rear of the coach. Here is a photo of the assembly you have to tap into.