It could be exploited by players selecting another of their group as a target and taking potshots at random ships.
One possibility that springs to mind - if both the player and the inadvertent target are targeting the same ship it could be considered likely that they would not deliberately hit each other (as they would appear to have common cause). However, this could also be exploited by one bounty hunter deliberately hitting another while they are both targeting a third ship.
The main problem with dealing with friendly fire is that the game cannot possibly determine player intent - and therefore cannot determine whether a shot hitting a ship was deliberate or not.
You are correct. The thing is any system can and will be exploited.
The current solution though is too blunt and too broad, and can also be exploited in pvp between two players as one can hide behind an npc ship.