so apparently you work for GM, ill abandon my search for that harness because obviously you put in a lot of effort lol
question though, the USB plugs you are trying to get working, would it not be easier to just get a identical plug setup as the one that is inside the center console with the 2 USB, input and SD card reader, get the proper plug and basically make the OEM harness split to support 2 identical plugs?
in theory, USB plugs can be split, we see it all the time on computers with a Y split adapter so you can plug in a mouse and keyboard and a USB key, or the keyboards you plug into 1 USB output and then it has 2 or 3 more USB plugs on the back of the keyboard for USB keys.
essentially that is what you would be making but for all the supported outlets in the one plug.
Just a thought.
great job with all the work to this point and documenting it, ill be following it once i decide to buy this console.