Yes, the simplest and most effective solution for the TAG would be a temporary NARC effect (not affected by AECM and EMP). For 3-5 seconds may be. So, it still should be maintained on target, but it will forgive mistakes. Right now TAG is just for teh lulz.
I have advised a change in lock-on mechanism for all long-ranges missiles. The main point is to make missiles (and LRMs in particular) hit better, but take more skill to use.
When the lock is started, a circle appears on the screen. Player has to keep enemy in the circle to get a lock. As a lock process goes on, circle gets smaller and smaller. If target leaves the circle, lock is failed (Player has to restart it). At the end, circle is just the size of a mech 1000 meters away. So, getting a full lock is hard. But player can fire missiles without a full lock, but in >25% state of a lock. A percent of lock acquired before the launch affect the turning rate of missiles (and scattering, if it is possible to code). So, on 25% of a lock, missiles turn speed is about 70% of what it is now. But at 100% of a lock, turn speed is 150% of what it is now.
GECM slows down the process, crouching, BAP and BHP make it faster.
The result would be:
1) Wow! Missiles require skill keeping enemy in crosshair precisely to get a lock.
2) Missiles are actually capable of hitting fast things with 90-100% lock.
3) Player can fire missiles even if they haven't acquired a full lock. E.g. - if enemy is moving to the cover.
4) Summing it all, missiles SUDDENLY become an effective weapon.
The process can be explained as computer reading sensor information about the target and uploading it in the missiles' warhead. The more info missile has about the target, the better it can track the target. But to get more detailed info about the target, front-mounted sensors should be better and better positioned on it.