I miss the options other space sims (X-Wing, Wing commander etc.) had:
Target Wingman's Attacker - especially useful would be our Fighter's Attacker, those pesky Missile boats...
I think wingman's target does default to whoever attacked, but could be wrong. But it would need 3 additional keys if it wasn't select wingman first, then target's target, since you have 3 wingmen and you can have them engage multiple targets.
EDIT: As a sidenote, although it would probably make the UI really busy, the game could color code engaging enemies depending on which wingman they are attacking.