So how are you handling the use of the Ion Cannon Batteries and the Redirect Token?
Ion Cannon Batteries reads as a Blue Crit Effect; "Choose and discard 1 command token from the defender. If the defender does not have any command tokens, the defending hull zone loses 1 shield instead.
Would you say the lost shield is locked to that hull zone, or can it be taken from another hull zone via a Redirect Token?
Obviously, if the hull zone has no shields, you can't take anything away, so if there's no shield and no command token, you do no damage whatsoever.
Crit effects are applied outside normal damage resolution, so it should always be the defending hull zone.