Switching Keys/Ignition
The wreck does have VATS on the key and all that.
A: Swap out for another VATS lock cylinder and force the PCM and BCM to relearn. Not too hard...
B: Swap out for another VATS lock cylinder and program the PCM to ignore the BCM when it complains you didn't insert the right key.
You may need a battery charger and a couple of beers.
GM does it that way to ensure someone can't just cut the same key and steal the car in a couple of seconds. The modules will refuse to relearn until they trade messages numerous times. Enough to where there is little chance someone can do this to steal the car and not get noticed.

