Imagine this: you start a game as one man. No resources besides his job, maybe some income his dead uncle left him, and an ambition.
This man's ultimate goal is to rule the world. And he must do so by any means the player wants. If he currently starts in a system that he dislikes, he can either try starting a revolutionary group, or else try gaining ranks in the system and eventually running the place... into the ground.
He would then take his country or lack thereof and repeat for different countries. His past actions would reflect on how easy it would allow him to do in the next country- if he has a history of sabotaging dictatorships, he's most likely to be viewed at least as an enemy to be watched on in a neighboring dictatorship and is unlikely to make much political headway. Conversely, destroying a dictatorship would put him in high standards for democracies.
Near the end, you could go control a dozen countries through favor with dictators, then flip the government's role entirely to get favor with the remaining democracies around the world, and once you have a position of power in them, lead a private coupe with some brainwashed forces left over from your dictatorship to take over and dominate the planet.
By the very end, you could openly switch between democratic and dictatorial roles, purely to watch people scurry around, and they would be powerless to stop you because you'd have control of the military force needed to easily stage a coupe on any weak government structure built up anywhere.
That, I think, would be a pretty cool game, although that's only a rough sketch I'm imagining.