Pete,Updated wiring diagram attached:
That is a very nice and professional looking diagram you have made!
Now, I may be confused or just plain uninformed, but I struggle a little bit with the kill switch setup you have there, and how the Aux output is controlled.
But let's start with the ignition lock first. Battery + is on the red wire to ignition lock, then when the key is turned, it is on the brown wire to "Lock" input on the M Unit, which sort of turns the unit on, correct?
But how is the Aux output switched ON? After all, the kill switch receives +12VDC on the brown wire from Aux out, and proceeds to operate the relay, which then disconnects the Con input from ground, if I understand this correctly.
What I would have done, is to supply the kill switch directly from the ignition lock switched out (brown), without involving the M Unit. Then used the relay to control ground or no ground to the relevant input channel.