Tourist:
The Sully case is another on(e).
The computer would not be trying to guess whether he could make the runway. It would know. It is very simple physics for the computer.
And the computer will respond with a ONE or a ZERO.
ONE, No problem. It steers for TEB with optimum configuration - Gear up, if necessary.
ZERO - Now what? Would it steer for the Hudson, and avoid the watercraft? What database would apply?
Seems to me the Cat3a-configured, pilot-optional airplane will not be capable of flying safely in a strictly VFR environment.