No idea how hard that would be to code, but we haven't seen any weapons that introduce any kind of "stun" effect. It'd take a little play-balancing (maybe the duration of stun is in proportion to damage done as % of a ship's total damage), but has that sort of thing been tried before?
That sort of effect does already exist (e.g. Zenith Paralyzers, Riot Starship "tazers", EMP warheads/guardians, etc.), but not on turrets so far. It's a fun, useful, and sometimes very powerful effect, depending on how long it lasts and how easily/widely you can distribute it. Generally the things that cause it do negligible damage themselves and serve a support role, so they have to be paired with something else to actually finish stuff off, which prevents them from being
too strong on their own, along with a decent number of things being immune to paralysis.
Maybe a "Point Defense" turret that actually has a 50/50 chance of shooting down enemy missiles and also can do modest damage to Swarmer, Light, and Ultra-Light craft? Again, not sure how easy or hard that would be to code the "Missile defense" ability, as it's a new dynamic in the game (I think), but it'd be cool.
There are already a few different ways to provide defense against specific damage types like that. The most obvious/straightforward is just immunity to missile ammo, which prevents being shot at by missiles in the first place, but that wouldn't affect any other surrounding units. However, there are things like the counter-sniper turrets that provide protection from sniper shots to a certain area. I forget if something similar exists for missiles, whether on a structure or a ship, but it's the same thing, just for a different ammo type, so that should be straightforward. Also, there's a bonus ship type that I forget the name of that has an ability that reduces the damage of incoming laser shots to 1/4 (or something along those lines), which I think affects everything within a certain radius of it, so that's another already-existing mechanic with a similar effect that could be repurposed.
I wonder if there might be a way to introduce a Turret that did modest Engine Damage on top of normal damage? The Grav Turret is a nice different flavor than the Tractor Beam Turret or the Logistics Station's ability, but why not introduce a turret that actually damaged AI Engines a little bit?
As Ranakastrasz says, spider turrets are the current way to go for that. They're the upgraded form of sniper turrets. They're cripplingly expensive early in the game, but they can also be quite awesome to have around sometimes when you can afford to. They just hang out in the back of your system, well out of range of being attacked by anything, and shoot the engines off anything that dares to try to get through your other defenses.
