Visual aid for what we have:
And what my choice for 10 more civs would be:
1 - The Byzantine Empire (Early game defensive civ)
A large, powerful and well-known empire, represents a large area in both Europe and Asia, culturally distinct from every civ we have right now and there aren’t any Mediterranean civs.
2 - The Almoravid Empire (Agressive Rush civ)
A very large and powerful empire, represents a large area in both Europe and Africa, culturally distinct from every civ we have right now, and there aren’t any Maghrebi civs.
3 - Spanish Kingdoms (Defensive and Naval civ)
You cannot have the Almoravids, without adding their eternal enemy, the Spanish Kingdoms. This civilization should have a very cool and unique mechanic where you start as “Asturias” and then as you Age-Up you can become the several different kingdoms in Medieval Iberia.
If i had to pick a single kingdom, I would pick Léon, since it existed for the longest and almost unified the rest of them at some point.
4 - Italian City-States (Turtling and economic civ)
If we could work out some way of representing several different city states using a single faction, then this would be an option. I tried to sketch it as well but it is much harder to achieve than with Iberia.
If i had to pick a single civ i would pick Venice, but in that case it would also drop to last place in the priority list, as Italy is already partially represented by the HRE.
5 - North-Sea Empire (Agressive naval civ)
We lack any scandinavia civilization, this one would be a good representation of both Norway and Denamark without naming it something silly like “Vikings”
6 - Kingdom of Hungary
7 - Grand-Duchy of Lithuania (Cavalry and aggresive civs)
8 - Kingdom of Poland
All large, long-lived, powerfull and culturally distinct realms in Central/Eastern Europe, which is currently lacking representation.
Maybe I am going overboard with civs in this location, but i couldn’t think of any civ that could represent all of these combined (Maybe the Poland-Lithuania commonwealth, but that is more Early-Modern than Medieval)
If i had to pick a single one of these i would pick Lithuania because we need more pagan civs. (And i would proceed to add the top 2 in the honourable mentions)
9 - Empire of Abyssina (Defensive civ)
We need at least one sub-saharan civilization.
10 - Khmer Empire (Economic civ)
We need at least one SEA civilization.
Honourable Mentions:
-Ashikaga Shogunate
-Goryeo Dynasty
-Aztec Empire
-Inca Empire
-Malian Empire
-Majapahit Empire
Reason why they don’t make it to the top 10: Too isolated from the other civs to make sense to interact with them.
New 4 campaigns:
1-Reconquista (Longest, and second blodiest war in Medieval Europe after the Mongol conquests, synergises well with the addition of the Spanish and the Almoravids, criminally absent from launch).
2-Northern Crusades (Way cooler than the Holy Land crusades, and much less known, would feature the Lithuanians and Poles if they were added)
3-Arab-Byzantine wars (Would give the Abbassids a campaign, which they lack)
4-Something in Asia, maybe some conflict between China and the Khmer.