Fixed weapons have been frustrating from the beginning. I understand why they exist, and why they are the way they are, but even in real life there is "convergence". I've noticed that some fixed weapons will move their aim-point a tiny bit, especially when a subsystem is targeted, but this only really helps with very small ships; on larger ships, the weapons are simply too far apart for it, which means hitting smaller ships with two weapons is difficult; hitting subsystems with more than one simply does not happen.
What I would like to see is a variety of options in the outfitting screen to adjust the aimpoints on fixed weapons. For example, a pilot of an Imperial Clipper would be able to adjust the aimpoints on a pair of fixed beam lasers on his wingtips inward to compensate for the extreme difficulty a Clipper is notorious for when it comes to hitting any target with more than one of its weapons; someone who was frustrated with his Eagle's difficulty in hitting subsystems with all three weapons could angle his dorsal mount down just a fraction of a degree; someone who wanted to mount quad pulse lasers on his Fer-de-Lance could have them adjusted in so that they all met at a point exactly 2km from his ship.
Setting the convergence on electrically-controlled weapons has been an issue for the air forces of the real world since just after the first World War; in our world, of course, this is something that military command organizations decide for all their pilots at once, but it makes sense that in a galaxy full of armed, privately-owned starships, any individual pilot mounting fixed weapons would be able to have the adjustments done to his own personal specifications. For an appropriate labor charge, naturally.