Right now all the building in Elemental occurs within a city, and the cost of building a city is high (using up valuable essence, and the oft-discussed escalating cost of upkeep).

I was thinking that the use of Watchtowers could/should be changed.  While watchtowers might serve a purpose within a city, it seems they would serve a bigger purpose, and be more "true to life", if they served as outposts - i.e. buildings that could be scattered far from cities to keep an eye on remote borders.  Have them cost only money to build, not essence; have them buildable anywhere in your territory; and have units stationed on the same tile recieve some type of defense bonus.  They could remin buildable only by the sovereign, to keep them from popping up everyhwere quickly, or they could be built by other units..I have no opinion on that.  But using watchtowers in this way seems more appropriate and useful to me.