Total war Warhammer - Wood Elves defending Lookouts far from the Forest

Wood Elves are unique in being able to capture any territory in the game, however the Lookout will only have a garrison of 5 Low-Mid tier units and unable to construct only other garrison buildings constructing garrison only provides a couple more units but loose the important economy/military boost that lookout can provide.

Is there any other means to protect Lookouts far from base other than stationing an Army there which will also increase the upkeep of existing armies?

EDIT

I have accepted an answer as it does answer my question but I still do hope there is a possibility there be a less known way to increase defence of lookouts.