The palisades_watchtower is, rather confusingly, not a tower: it is not garrisonable, has no attack, and no significant vision; its parent is template_structure_defensive_palisade.xml. The same is true for the palisades_outpost.
The desired template is palisades_fort, which is not a fort, but a tower, it has template_structure_defensive_tower_sentry.xml as its parent.
The templates follow the naming scheme of their corresponding art actors, which were added in rP9915 and last touched in rP12183 (eight years ago). From left to right: watchtower, outpost, fort:
This patch renames palisades_fort to wooden_tower, replaces the palisades_outpost and palisades_watchtower with the wooden_tower in the few map files that use them (most used the palisade_fort), and removes the palisades_watchtower and palisades_outpost templates, to avoid future confusion. The art actors are kept.