Well, given how the biggest weapon carried by the average crewman is a light blaster, and only about a third (at most) of the crew are actual soldiers, FourSev is actually pretty capable of tearing his way through the ship. But that's just food for thought. I highly doubt we're going to reach a situation where FourSev goes hostile. He can, however, commandeer your bridge and essentially do Den's job for him if he thinks Den isn't doing a good job. Dark Troopers have a pretty special kind of authority.