I came up with the relay idea as it is used in other electronic sub-systems in cars. I have been using the relay for over three or four years now. I really can't remember exactly. In summary, there are no adverse effects in the module communicating with the other systems (radio, navigation screen, steering wheel commands, etc.) with this mod. No side effects in its memory or configuration either. Only side effect is the module is totally with NO power.
I created a PDF with all of the information for the mod, I also included a Radio Shack part number for the relay. I went with a simple solution because of time. However, I was looking to replicate the design of the module which should stay ON up to 15 minutes after the ignition has been set to OFF. This can be made with a diode, a resistor and a capacitor as a simple timer operating on a low voltage (1.5VDC) relay instead of a 12 VDC relay. Anyways, I asked myself, How many people (including me) stay talking on the car's BT with the vehicle totally OFF? That is why I opted for simple: ignition OFF = BT OFF. Ignition ON or ACC = BT ON.
datmdx just found and attached the initial file I posted. I will post the latest file with more information.
Did I addressed your concerns at this time?