Since the mic in line is unused, you would only need to snag one more line from somewhere else.

Couldn't the serial connector on the wire loom be removed for this purpose? Wouldn't that provide enough free pins ?
I wouldn't want to give up the mic connector. Who knows, someday VR might become a possibility still (I'm still hoping), and I would hate it if I lost that possibility then just because I disconnected the mic connector at one time.
The serial connector however, from that one I'm SURE I'll never use it in the car anyway.