At my last airline employer in the '80s, crew would report to dispatch and be taken airside in a crew bus or maybe even walk to the hangar and taxi over to the gate. Airside passes would have to be worn.
It would take quite some doing to put aboard an imposter crew on a scheduled flight and I'm not about to make helpful suggestions on how this could be accomplished. But assuming the imposter crew got control of a scheduled flight, they would
not need any weapons or explosive devices to do serious damage.
The problem for security posed by crews of several different operators, especially foreign, arriving landside is that they really have little means to know for sure that said person in a uniform is a genuine crew member or somebody on a secret mission to accumulate a critical mass of explosive toothpaste
Better would be a crew reporting office equipped to properly identify operating crew and send them on their way once properly identified.
Flight crew especially needs to be focussing on the coming flight and not being gotten into a stew over the umpteenth tedious discussion over the hazardous nature of tookits, toothpaste etc
Perhaps the Comair investigation needs to check on how the crew fared going through security.
In fact, aviation accident investigation methodology does address human factors and should add possible rankling encounters with security as a factor to be included in the investigation.