I'm sure Vincent will give you a better and official answer, and damned if I can find the reference in the preapocalypse book, but there's a part that says that gear should follow the same prescriptive/descriptive vibe as the various count downs. Meaning, if your driver finds a machine gun in-fiction and says he's strapping it onto his car, change his car's stats to have a machine gun. Likewise, if he takes an improvement to have an armed car, then say how that happened in the fiction. Also, with 'take away their stuff' and 'make them pay' I think those could cover changing a piece of gear's state in various ways beyond just making it appear or disappear.