I suggest that a player be allowed to garrison any inner location of a
province he controls.  This would allow players to replace city garrisons
that are destroyed.  It would also allow players to protect empty structures
such as inns & towers from attack by savages or others.
The complication would be that such garrisons would require hostile/defend
orders.  One choice would be to set them for admit all/defend all, with the
owning faction being allowed give & get per standard garrison orders.  This
approach would serve to protect the structures, and should be a
straightforward addition, as the neutral city garrisons already do this.
--Carol & Erik Gunderson