Trailer brakes/towing questions

[OlyS4]

Hi all, I've searched and read all existing posts that I can find regarding towing, and still have a question on the trailer brakes. I'm in the market for an '08 3.0 to replace our '02 3.0, but will want to tow a small ski boat with this one. It seems that I will be able to tow around 3000lbs just fine, and it sounds like the BMW tow hitch is the way to go, although I don't know if it makes a difference if it's installed by BMW or not, as long as it's done correctly. I will mostly be towing short distances, but occasionally will want to take the boat over mountain passes for vacations.

My concern is braking, since the vehicle braking is only rated at around 1600lbs max tow weight with an unbraked trailer. Some previous posts referenced a factory harness that could be connected to trailer brakes, does anyone have any first hand experience towing connected to the trailer brakes this way. When towing and connected this way, does it feed some type of info to the ECU? Is this mis-information, or did I possibly read this incorrectly? I would like to purchase a trailer with the trailer brakes to be safe, but don't want something wired insufficiently or incorrectly. I would like the whole install to be very clean.

Thanks!