Add a PT door to the back of the bar that opens up a door to a PT. The opening of the door takes 5 seconds (by pressing "E"), and the door is held open for another 5 seconds. It then closes, and you are forced to open it up again if you would like to use it again. Just move the logo on the back of the bar down a bit and have the logo be the door that opens up to a small version of the PT.
It's not using the pt through a wall. It's not too advantageous. It will help stop many SBH nukes to the bar and buildings near the bar. It's a good compromise to not using a PT through a wall, since SBH nuking is undoubtedly more successful to the outside of buildings.