I'm working on my own campaign that takes place during FS1 era, and I've recently added a broader range of cap-to-cap turret weapons. For turrets, both Terrans and Shivans have standard, huge, and weak weapons, while the Vasudans have standard and huge. I've converted the weak weapons into anti-fighter turrets by upping the fire rate, and made a similar weapon for the Vasudans. I also created mid-turrets that reside about half way between the standard and huge, for each race. I also made a terran mega turret that does 200 dammage and has an impact exposion. I even made (or adapted) sounds for each one, by speeding up some sounds or merging them with others.
For the mid-class turrets, I basically needed an anti-cap gun for the front of the Cain and Fenris, as I don't like them just using the same guns as on all the rest of the turrets for their primary gun. I have also gotten in the habbit of loading the forward turret of the Leviathan and Lilith with Terran Huge and Shivan Megafunk weapons respectively.
Later!