This is much needed as there are many aspects to a culture and how the peoples of those cultures come together to form governments. This is especially useful when creating planets vastly larger than our own with billions of different peoples and hundreds of sentient species. For example, take the Formics (Buggers) from Ender's Game; their government, if fleshed out, would not only be "queen bug is leader bug", but would also be strange and extremely unique as it is even mentioned that many Queens worked together. I believe it would be extremely useful to even be able to create a form of government from the ground up, giving it your own name, the systems in which it operates, and how the citizens would interact with it.
It would be neat to have an option that was essentially "fill it in yourself" option so that individuals who want to use those lesser known systems could. I've never heard the term diarchy, so i could understand why that might not be something to roll out site wide as it might be extra confusion for a casual user. But a blank section within the organiszations (so it has the structure without using a completely blank article) could be an option
The types of government system and economic system lists are both pretty limited, it would be great to see these expanded.
I wonder if on some of these "type" lists it would be possible to add a "suggest New" on the list itself where someone could request directly on the list when we would like something added. Something outside of the ideas and improvements, different workflow, response, etc. Org type is just one great one where I would love to see this.