My thoughts:
I think it would be a huge mistake not to implement lock-on missiles as they are a part of the Star Wars cannon [...]
I don't know about the canon part. While in the Prequel Trilogy anti-fighter rockets are shown to be homing and long-living, this is contradicted by the inability of the weapon electronics of the Original Trilogy to hit even a stationary five metres wide target. Laser cannons, too, need quite some time to lock on to their targets before starting to aim. 'Computers', in the words of an Alliance pilot, can't hit a target five metres wide, which logically implies they can't hit a moving target that size or smaller either.
So when I think about air-to-air missiles in Star Wars, my thoughts spring immediately to the German R4M 'Orkan' air-to-air missiles used late in World War II - unguided rockets without too much effect. Of course torpedoes could be set to fly through pre-programmed waypoints, but we actually don't know if they really possessed homing ability, as they were meant to destroy large, slow-moving targets such as corvettes and frigates.
Of course, if you want homing missiles, you can easily say they're a new technology fielded at some point after the Battle of Yavin (it's not like humans learned to make and use homing missiles after World War II), but even then, they should perform like real-life First Generation missiles.
"One of the bitches actually gave birth while she was attacking, and her puppies joined in on the carnage."
--the awesomeness that is Boatmurdered.