I'm not really sure what the big issue here is:
Basically, some people want the big anti-cap guns to fire at fighters, but there's also a desire to have them move slow enough to avoid. Well my question is, if they're slow enough to avoid what's the point of having them target fighters in the first place? In FS1, the Anti-ship guns are slow moving blobs too. And they're _easy_ to avoid. It's much more annoying when a ship has a fighter-type gun on it, because it's hitting your with every shot just about. And yeah, it's one more thing to think about. But if you want to give capships some more bite, give them missile launchers. Which I believe they already have.
If your fighter is sitting motionless, shooting into a helpless capital ship with stripped AA guns you should be complaining about poor mission design, not game mechanics.
And if you want to talk about realistic, there's always the question of traverse. If the turret resembles that of a WW2 ship, as it's supposed to, its ability to rotate and bear towards its target should be somewhat slow. If a turret is design to attack slow moving targets, generally it's going to have the capabilities to hit them and not much more. It would be hard to track and aim at fast moving fighters, let alone connect them with a slow moving shot.
As for what to base WC:Sage upon. Well Wing Commander, is fundamentally a game. Not a movie. So if you make a mod based on WC, it should be based on the WC games, not the cutscenes, not the movies, not the manuals. The people who make the cutscenes aren't necessarily the people who make the game. FS2's intro is notorious for being non-canon for a multitude of reasons. B/c the movie was made by people other than those who made the game. Just as the WC manuals, in-game Live Action, and the WC cutscenes are probably made by people who did not develop the game. If the same people, do three different aspects of the game, it takes three times as long to produce. That's why you have teams separated into departments.
It's the same as when people try to port Imperial Star Destroyers to a variety of table top wargames, there's always someone saying "well this book says it has 60 laser, 60 ion cannons". Well Star Wars is fundamentally a movie, not a book. And no ISD in the movie fires anywhere near 60 laser cannons. Though at the same time you can see from the model that the ISD has four major turrets on either side, which never fire, but are still quite visible.
And if you want something very realistic, then you shouldn't even be playing the game. Because odds are, there will be no such thing as fighters in space combat, not manned ones anyway. The only reason fighters play such a large role in naval combat of today is something called the "horizon". There is no horizon in space.
Take a step back, realise it is just a game and instead of saying something like "The Kilrathi cruiser was too easy to take out, it's guns were too weak." say "The Kilrathi Cruiser was too easy to take out, it didn't have enough fighter cover". Improving the game is all nice and good, but there needs to be considerations as to what is doable, and what is worth doing. If a change is intended to make the game more fun, can that level of fun be accomodate with improved mission design for example?
Yadda yadda.