Excellent work! This will be really useful for finally creating that elusive gunship class.
I got an couple of ideas on improving the user interface:
The basic idea is look-and-shoot. The turrets aim where you look. The problem is, where you look is actual a point in space, and this could be anywhere from the tip of your nose to the next galaxy.
So we need to tell the guns the range of where you look and vice-versa tell the player where the guns aim.
(Your "ghostgun" does a very clever range calculation. However I have a feeling this data would be also available from the targeting code that generates the shooting reticle, so a code modification - or hook just for your script - would be more than justified in this case).
What we need is a visual cue. The set of cross-hairs should be scaled according to the range (from the ship) the guns bear on. If this crosshair is the size of the average target (fighter for instance) then when you slew your view onto a target you will be assured a hit when it "boxes" the bogey.
If we want to simulate an actual "lock-up" (which would also be handy as it leaves us time to do a ghost-shot) a different reticle should be displayed while calculating range. So we have a reticle scaled to infinity without a target, a lock-up reticle, and finally an appropriately scaled reticle. This creates a "flashlight" effect, so the player will immediately feel when he has something in his sights.
To simulate turrets without infinite tracking speed a different set of cross-hairs could be actually rendered for the guns themselves. This set of cross-hairs should always point at the point where the guns are actually aiming. So by waiting until the second set catches up you can tell the player whether the guns are locked up or not.
If you're firing ballistic (ergo not hitscan) ammunition, the same code could be used to generate a set of similar crosshairs for a set of ranges so they would give the player a bullet trajectory. This could also be done on a per turret basis, so widely spaced turrets could also be visualized.
Finally the code could be combined with the convergence code - as far as I see it already is in a matter of speaking, since the turrets "auto converge". In a primitive setting - or at a CIC type gamplay - one could set the conversion or target range. By doing so with the mouswheel and with the above visual cues we have a fast and entertaining gameplay.
