That would be awesome, but for this sort of thing I'd like the ability to have the laser integrated into the secondary weapon rather than used as a primary. I'd finally have laser-guided bombs in Wings!
why have tertiary weapons never been completed? this is a perfect application for it. for me im thinking about either scripting an 'infrared beam' which is essentially a straight line with no visible graphics. i also thought about using a sensor turret, which would have a targeting beam equipped, but that kinda takes out some of the skill required. im not sure if weapon collision hooks work on beams, but those maybe could be used to report the impact location to code which guides the missile.
scripting needs a lot of work i think. right now scripting essentially provides a way to hack around certain behaviors and features in the game, what we need is a way to make the game work with scripting. meaning that the c code wants to do one thing and is allowed to do it, then when the script hook rolls around, all that work is cast aside wasting that cpu time, and script is run to do things the way i want them to be done. my physics scripts are a good example of this. i essentially go "that velocity is wrong, gtfo of my way while i punch in my own vector". for missiles i say "its a hear seeker with a turn time of about a million." the game runs all the code needed to put that heat seeker on its ways then i go "nope do this instead" its all brute force and little efficiency, no matter how good your lua code is.
better way is have a 'scripted' seeker type and a hook that runs when a weapon of that type is found. for something like physicsi need more of a general override and a hook (or multiple hooks if theres an init or code which needs to run after other things have happened). you would be exposed to all the relevant vars, thrust forces, collision forces, etc, then i compute forward velocity and angular velocity. i could rant all day about the inefficiencies of scripting and how many of the features i script in feel like cheap dirty hacks.