thats doable. do some math to find out if the ship is in your cone. your weapon would be a smart heatseeker (theres a table flag to give heatseekers more brains iirc) or aspect. all youd really need to change the missile target to its velocity vector when the targets not in cone.
laser guided would be cool as well, simply set the missiles homing location to the point in space where your laser vector intersects hull. sorta like ssm but where your missile is being launched from your own ship and will chase anything the laser reflects off of. determining that would be difficult, as youd need some collision detection (quakec had traceline, give it a vector and it would follow it till something was hit, and return the distance). i know theres hooks for weapon colisions, but do they have access to the colision location vector and do they work on beams? im really only familiar with 3 hooks at the moment so i probibly could only make this work in a hackish fashon, such as using the players velocity vector times the target distance or more accurately a player unrotated (0,0,target distance). of course with large targets this would work poorly at best.