:: You raise a good question. ::
Do you think that these situations have not been gamed out? (Rhetorical).
There are several scenarioes of “attack” that can physically disable POTUS/CinC.
Are there scenarios that don’t physically disable him from his appointed duties (again, they are 2-fold...POTUS and CinC)?
I imagine that things in that category were war-gamed even before 911. Bush ran things from Offutt AFB outside Omaha until it was safe. They probably have improved on that in the past 21 years.