Well, this sounds like I'm talking to myself...lots of viewers, but no responses!
Anyway, in further investigation, I was told that the Right Connections trailer interface wiring kit once installed (on a UK BMW anyway), does NOT require any recoding of the vehicle, and provides all of the factory trailer functionality: PDC off when a trailer is attached, enable vehicle trailer stability program, and makes a zoom with centerline video function available. They have no way to verify the same would happen to a US spec vehicle, and thus, I'm a little leary about buying it.
I also found and read the trailer installation instructions on the BMW X3, and the last step there says to reprogram it. The BMW wiring kit is nicer, since it just plugs in.
Anyone have a trailer hitch installed on their GT? Do you have a trailer wiring kit installed? Do you have any of the factory trailering functions? Are you in the USA or elsewhere? Did you have to reprogram anything?