This suggestion does only work with LRMs unfortunally, but since our SRMs are unguided I'll make it anyways.
If your mech mounts the Artemis IV FCS you will have a new entry in your weapon list. You can assign the Artemis IV to any weapon group like you could any weapon.
If you target an enemy with your rader, it is in your frontal arc and your LOS you can "fire" the Artemis to instantly gain a lock. This lock is valid as long as the enemy stays in your front arc and in you keep it as your target.
If you break this lock the missiles will lose their tracking and fly towards the last position were the enemy was still locked.
Pro: Locks can be gained instantly.
Con: You can't lock onto enemies that can not be targeted. Can not be used in conjunction with poptarting and you can't take cover after firing the missiles.