Many GM vehicles use the fused BAT power circuit to also power the +12V at the OBDII interface port. You may not just be dealing with a couple convenience power outlets.
Perhaps it would be easier to simply remember to unplug phone chargers and other non-OEM equipment when exiting the vehicle - It's a little like remembering to set the parking brake. Any of you who are pilots might be thinking the same thing as I am, in that there is always a routine when entering and exiting a vehicle, and it simply becomes habit. Then again, anyone can get a drivers' license but not everyone qualifies as a pilot.
An alternative to the hacking up the fuse panel wiring and bussing could be to break into those power outlets and feed them from the orange ACC/RAP power system. There are usually junction blocks with taps to the RAP power system which would make is easier.