Well, considering the almost unlimited variations on governments that can exist, why not break it down into its components? From what I see, the fundamental piece of a government is an Official, which I am using as a blanket term that can be modified with relevant tags. Officials can have tags relating to how someone can become one (election, inheritance, delegation by a superior), qualifications (skills, relative power, nepotism, social class, prestige), responsibilities (external diplomacy, military command, finances management, providing military aid to superior, providing taxes to superior, law making/enforcement, voting). There could also be values such as rank or authority, a list of subordinate positions, and such.
This system can feasibly be used for all sorts of government structures, from monarchies, to democracies, to republics, and every other government in between and beyond, as long as they include an Official in its structure. Heck, this might even be expanded into any organization, including religious groups, guilds, and the like. This might actually not be as complex it might be in an official release, knowing the nature of DF.
Just a thought. I have been thinking about it for a while now and I wanted to share this idea.