This is what the AoE 2 map of Europe would look like with the addition of the four final European civs I have proposed above.
(for Serbo-Croatians civ I used the coat of arms Sirmium - a Byzantine administrative unit [theme], which existed in present-day Serbia, Croatia and Bosnia and Herzegovina in the 11th century. Its capital was Sirmium [today Sremska Mitrovica])