Definitely don't restrict all combat equipment. It's just not that kind of setting. People wander around with guns, and some people (mercenaries, adventurers, etc.) probably have big guns, and other such heavy weaponry. Just having them isn't against the rules in the setting (unless otherwise specified).
A trap on the front door is definitely dumb. I've wandered into random office buildings just to see if I could use the bathroom before, and it'd be kind of unbelievable to say that nobody has managed to set a trap like that off.
I don't actually have the book in front of me right now, so I don't have the layout of the place, but maybe you can adjust things around a bit? A public area that's relatively safe in the front, with the trap moved just past an "employees only" door, or something.
...An extra couple of rooms (and more importantly: Doors) in the way also helps explain why the cops might not crash the party. If the PCs go in guns blazing right off the sidewalk, yeah, someone might get alarmed, but if there's a few rooms in the way you might rule that nobody outside hears it over the hustle and bustle of the city.