If the tractor beam had a lockon feature like the missles then it would make hitting those small fighters very difficult in a large capital ship.
I think this would be a great add because then one could tow a rock to a processing facility, tow a damaged ship to a station, help redock a ship, or, my favorite, hold a ship for boarding. However, 3 things:
1) A tractor beam should not be able to lock on to a ship with shields intact. Also, if a tractor beam has locked onto you while your shields are down, they shoul dbe prevented from regenerating.
2) There should be a bomb/torpedo style weapon for small bombers. High impact, long reload times, no ability to stack, and expensive. This way small sqauds could stand against large ships and do some damage.
3) Tractor beams should have a seperate control computer and have to be built up just like all over weapons. This would increase the size of the beam. If a ship was to big for the beam to encompass, then it would merely slow it, not stop it, until some of the engines were blown out, and wouldn\'t stop shield regen.