Really appreciate you taking the time to make the review!
Like you, I bought a 6MT 3.0 a few years back. At the time, the only way to use the actual BMW method of trailer lighting was to either hope you get lucky in a junkyard (which was becoming ever-less-likely) or pay $400-500 for someone's old harness.
So I built my own and decided to sell them as well.
If anyone has questions on how to install this harness - or how to make it work with a brake controller - I am more than happy to answer them.
The Sterlingfrau is currently at the shop suffering from the effects of a botched clutch replacement, but once I get it back, I will make an installation video to show the trick to installing the harness without bumper cover removal.
P.S.: It's me, the seller