On the CM side you can check the logs and change the scores after the fact, but you can't look at a live report that says "Hey, dude, 10 pilots took off with 30mm instead" and eject them then and there.
It's not something you can regulate or prohibit, it's just something you can track after the fact. By then the damage is done.
There currently is no tool/feature to disable specific weapons options in a single aircraft and not others.
So? How do you think we enforce the other 99% of our rules? Punish those that choose to break the rules. Furthermore, if I catch someone in the logs, their kills or damage is thrown out, and that individual is dealt with. You're correct in saying that I can't turn off a certain ordnance configuration, but I'm telling you right now as an Admin CM for FSO, I'd have no problem including a G6 in a mid-war event, even though a 30mm
option was available.
My personal opinion on the matter, as it is with every other aircraft in-game, is that if it was available and saw combat, it should be represented in-game. Let the CM's determine how we're going to regulate something after-the-fact, and give us all the aircraft and different configurations as possible. It only adds to the game.
For whatever it's worth...