I was thinking something similar recently, but it would have to be done a bit differently I think. I was thinking a ship should be able to 'track' up to X number of targets, similar to how it marks asteroids on your HUD when they threaten an Escort ships, except these would be bracketed a different color.
In a way, this already exists: the 'Hotkey list'. In mission, press F3. Assign ships to a hotkey (F5-F12) and then go press that hotkey back in game. I didn't know this existed until two years ago! I toyed with expanding this a year ago and made some hacky progress, but haven't had time to do more.
It would just pick the closest hostiles or the ones with the highest priority.
That's the trick. I couldn't come up with a good way to keep track of the ones with highest priority besides doing it manually in-flight. Or having it select EVERYONE

I did come up with new keys for multitargeting "all ships in target's wing", "all ships attacking target" and "all ships attacking me". Only problem is, we can't add any controls until the new pilot code in 3.7.
Now, if you had a swarming heatseeking missile, perhaps it could use this list to throw one missile at each target the game has bracketed for you. Imagine how awesome it would be to be able to launch a volley of missiles at 4 shivans emerging from subspace in their tight little formations, all at the push of a button (from behind if you know where they're coming from in advance even
).
Indeed, this sounds awesome and I want it to happen. I wish I had more time to try and work on this myself, but I'll be glad to help someone by pointing out places in the code that would be involved...
It would be cool for a ship to be able to track multi targets, but I don't think that the targets she's tracking should appear on your HUD. It might get distracting with so many brackets on screen.
Oh it's distracting, but it's also frelling awesome, especially if they have lead indicators. Imagine: flying at a wing of bombers, firing primaries at the closest one while locking on another with secondaries.