What is the end state you are trying to achieve? It sounds like the idea is to be tasked randomly to hit various targets but at the end of the day, all the targets are attacked. If so, you just need to use some flags and Boolean logic.
Not being assigned the same target twice can be done with a trigger that looks to see if something at the target is not damaged or dead. So if you had an SA-6 site as the target, check the StraightFlush STR radar unit and a couple of launchers. Pick one or two units per target. That way, the system can reassign you to the same target if the target hasn’t been sufficiently damaged. But if it is, then it needs to run its random flag game again.
It’s all Boolean logic which makes my head hurt but in the end you can make almost anything work.