Just some ideas to go with the Uniform Editor.

General Creator- something to allow you to create your own generals. Could be as simple as choosing from existing portraits/skins to creating a unique look. Why? Historical accuracy is great, but sometimes you need someone you can really count on.

More Revolution/Coup- a way to change the guy in charge. Perhaps take a great general, or some yokel minister, and elevate him to the top spot. Why? Some generals make better kings (or emperors) than the other guy.

Nation Name Change- as empires and kingdoms grow and change, sometimes a change of name is warranted. Why? Who wants to play the Kingdom of Snookles- Republic? Let us make the name more fitting.

Flag Editor- this goes with the Nation Name Change. Sometimes the old banner is just that- old. Let us make a banner that more suits our greater empire.

These are some ideas. I don't think any of them would be too challenging to add, and they aren't the terrifying mod tools that CA doesn't want anyone to have. They just allow us to add some more flavor to the game. I, personally, would definately pay for a DLC like that.