The Deep Space 9 station was given a series of upgraded weapon systems in a Season 4 episode, "The Way of the Warrior". Since the model had not been designed to have any upgrades... and in fact was not changed... they were shown as separate weapons pods that "popped out" from the main model.
There were, i believe, four models used to show the upgrades; i have three. A main docking arm was built with a trap door to allow the weapons to deploy; two rectangular stations that were the new weapons platforms; and a round "photon torpedo" firing unit. I have the first three and they're shown below.
The upgrades as shown on screen, firing:
The actual docking arm with trap door:
The "short" not yet deployed weapons upgrade:
The "long", deplyed weapons upgrade: