The current meta with the massively overpopping zergs makes the turrets anyway useless.

See a zerg approaching in the horizon? Man all the turrets in the tech plant gun deck and fire away! With the three AV turrets you can get some of the [insert attacking MBT] down when they wander off the rep sundy radius... In the 20 secs you have, before all the turrets are destroyed by long range massed vehicle fire. When you and your mates have repaired the turrets, they are just shot down again in a matter of seconds. And when you are finally out of their barrel rise angle, because they closed enough, they are also below your shooting angle.

To be honest, I've don't think the gun deck provides much help in the defense of a tech plant, except a little delay before the attack pushes in. And, when the attack pushes in, they can use the gun deck against those defenders who try to bring armor from adjacent hex.

So, in my opinion, this update just turns a (mostly) useless thing into non-existant.