I have three ideas to show. A scenario, an union and a civilization.
I would love to see a Paraguayan War (Empire of Brazil, Argentina and Uruguay vs Paraguay) scenario. Where Paraguay demanded some provinces of Brazil and if Brazil didn't accept, Paraguay declares war and demanded Argentina to join against Brazil.
Now the union, since the game has Australia-Hungary (James Cook) AoC 2 could have Austria-Hungary-Croatia.
For the civilization. I saw the leaders list and found Pepe so i think AoC 2 should have Kekistan