I'd love to see a 2-missile-attack-per-turn "massed launch" option, but I agree that that then puts you in "look, twin harpoons!" territory.
Forcing you to fire at two separate targets stops it being "take eight damage and die" which wouldn't be healthy for the game, but then managing the need for target locks makes it really awkward, necessitating something like Targeting Synchroniser or Redline spending time setting up twin locks.
As far as I understand, the Punisher's key trait was the head-on attack run - whether with bombs or missiles - as opposed to the hit-and-run techniques now used by SLAM K-wings and gunboats.
I would probably go with something like this:
TIE/IT
Title. TIE Punisher Only.
You may equip an additional [system] upgrade.
When you reveal a green maneuver, you may execute a free Reinforce action.
You must place the Reinforce token with the fore side face-up.
Cost: ?
I would say 0 - a negative cost is possible, but that's a massive chunk of capability; even if it's just Collision Detector and a free Reinforce token for head-on attacks.