So here are the civs that should be included in my opinion:
Iran (safavids,Qajars, Iran): We can all agree that Iran is top priority.
Berbers: (Zirids, Almoravids, Almohads, and the dozen Morrocan dyansities that followed): The Berbers should spawn with (settle): one city in Morrocco (whatever one is more historical; choices include Fez, Marrakesh, Rabat), Tunis, Al-Jazair and Seville in Spain (Seville because not only was it significant under the Muslims but also under Spain itself).
Central Asian Civ: (Ghaznavids, Seljuks, Khwarezmian, Timurid and Khanate of Bukhara): To represent a central Asian civilization is difficult task because most of the expanded into Pakistan, Afghanistan and Iran. Three of these dynasties are before the Mongols and two afterwards. So heres my solution:
Ghaznavids spawn in 950 ad: Cities in Central Asia, Iran, Pakistan, afghanistan flip to them. In game thats four cities: Merv, Samarkand, Sihraz and Qandahar. Their name changes to Seljuks and then to khwarezmian empire. then in with the spawn of Mongols in 1250 Merv and Samarkand flip to the mongols and the empire collapses.
In 1400 the Timurid dynasty spawns and flips all the cities in central Asia, Iran, pakistan and Afghanistan. 100 years later the Safavids Iranian spawn and flip Persia and Afghanistan. The timurids are left with Central Asia and their name is changed to Khanate of Bukhara.
This might sound complicated but basically its a spawn, collapse and rebirth. These mechanics can be tweaked for the Human player.
Minor Poland city: Just one city in poland (krakow or Warsaw) to slow down german expansion in the region.
German/Austiran separation: The Austrian should be called the Holy Roman Empire then German spawns in 1500 (as kingdom of Prussia) and takes Berlin and Frankfurt. Also the Austirans should found Budapest more often. This serves two purposes 1) more war in Europe 2) Accurate Austrian Ottoman Wars.
Egypt: should spawn in 900 ad as the Fatimids. (name change to ayyubid and Malmuks). They can flip Cairo, Alexandria, Benghazi and Tripoli.
Whichever ones u guys want in the game, post them and i will give info on spawn dates, flips, unties and building