I think you should release an expansion pack, call it the world politics expansion or something. The groundwork for the engine is done already. The UK, Germany, France and Russia all come to mind but I would not just do Europe, Mugabe would be a very interesting person to play as and against.
I know it means a lot more work but pick countries with interesting situations and or have a large gaming populace.
I probably won't be buying the game unless you do this, perhaps a standalone expansion that may also integrate with the last one, e.g. so you can use leaders from other campaigns through a menu or something.
Oh, and I know the answer to my question (biggest population), just wanted to make a point/suggestion.
Charles