I was thinking about the weapons in Starsector, and one thing that I noticed is that there are no PD missile launchers. I mean, there could be some in mods, but I haven't seen any in the vanilla game. So I got to thinking about how it would work, and this is (roughly) what I came up with.
It would be mainly anti-fighter, but could be used for missile interceptions. It would be fast, but very weak (maybe enough damage to take out a missile, but nothing more. It would have relatively high ammo (20-30 missiles for a small mount, capacity increasing with mount size) and would take up about 7-8 OP for a small mount.
It may not be implemented, but it was an idea that could work with minor tweaking.