First off, only the security forces have military training. And if they were really willing to allow civilians access to the armory, expect them to be pretty stupid in combat. They aren't military trained therefore they are cannon fodder. I also doubt there's a large enough armory on a civilian station to fight against a full invasion unless it really wasn't a civilian station. More armory space means less civilian facilities and/or space in general. If you made it larger for the space, that's a waste of money and time for something not militarized. 

Secondly, even if a station goes dark, all power shut off, doesn't mean it's unlocateable. Echo location, material scanner, life sign detectors, long range sensors can also pick up any kind of emissions created by certain power plants, and that doesn't only mean exhaust. This can be radiation or even hydrogen build up. 

Technology, 'tis a bitch.