I'm starting to think that a viable solution would be to have the AA weapons fire in a beam like manner.

Each battery could have a zone of engagement, and when the player enters the weapon's zone you would calculate where the player will be X units of time ahead of where they are based on their current pathing, apply a random offset to this point, and then start firing off a stream of bullets/lasers that continues on beyond where they are.

Give the player time to react and try to plot a route around the danger area, but as they start changing direction then have the stream of AA fire try to follow them, and keep firing until the player leaves that weapon's zone of engagement.

With multiple overlapping zones the player is then forced to plan their forward path on the fly, and when combined with being able to see the emplacements ahead of when they can start engaging you then as a designer you can develop patterns that become effective 'mazes of death'. Choose poorly and you could find that fleeing in one direction from one firing emplacement's arc will instead herd you into the arc of two or three more.