As I seem to recall, Corgarff Castle didn't become a fortress until 1748 when barracks were added to each side of the tower house and the star-shaped outer wall was built. Prior to that time it was a comfortable county house that belonged to a branch of the Forbes family. In 1745 it was used as a mustering point for the army, much as other fortified houses in the Highlands were used for the same purpose. In 1748 it was purchased by the Government and turned into a barracks, the better to police the area and (later) to crack down on smuggling.

Tower houses, despite their appearance, really are not defendable against a serious attack nor are they particularly spacious. While it might be possible to provide accommodation to half a dozen officers, the rest would have to sleep in barns and other out buildings, while the troops would pretty much have to fend for themselves, and would probably end up sleeping rough, outdoors.

You really need to read McKean's book to understand the declining military rôle of the tower house in Scotland. That said, for the purpose of gaming, you can make up pretty much anything you want to make the game interesting, and I doubt hooded men from the Scottish Castles Preservation Trust will come calling on you in the middle of the night....