I guess there's a reason we don't use the fire exit for unexpected entrances. Out of six attempts to get actors through there on cue, we have failed four times. For different reasons. We solved one problem and created another. It is time to rethink this.
We have used the front entrance in many shows. I think we can make that work. There is a speaker above the door, because it has been used so much, and it opens from the outside without the duct tape. That eliminates two of our problems right there.
Using the fire exit was a dumb idea. I abandon it without a qualm.