Most of the gun weapons in fs2 are energy based. Now, since we know that this makes them light-based weapons, that means that we should only be able to see them upon impact. Unless the craft have quantum-interlace sensors that can detect and show things faster than the speed of light, which they probably don't, gun fire should NOT be visible! Also, this might make swerving to avoid anything but missiles a bit more interesting.
While we're on the topic, though, why not try to make the levels of difficulty more and more realistic, since they'd be harder and harder as they approached realism?