Hi Flogi. I thought of some ideas for the Ibadi, Sunni, and Shia religions. Ibadi should be focused on trade (goods modifier, merchant, Trade steering), colonialism (Colonist), and naval power (Sailor modifer, fleet limit modifer). Oman (the only Ibadi nation) had expanded to occupy much of Somalia and Swahili Coast, and settled many of the islands of the Swahili coast.

https://en.wikipedia.org/wiki/Omani_Empire

Shia would focus on espionage (Spy Network Speed, Rebel support efficiency), fortification (fortication defense modifier), and military (Shock Damage increase, Leader maneuver, movement speed). Many of the main Shai regions reside in mountainous and defensible terrain (Yemen, Persia, Azeribaijan, Lebanon, Eastern Turkey, and Syria) and lower Iraq, east coast of Arabia, and India being the main exceptions. Due to the persucuted nature of Shia, often intellegence gathering and secrecy (hiding their adherence to shia islam) was necessary (possibly unlocking Infiltrate Administration early for Shia). Lastly, military, military confidence from intelligence allows for one to pick and choose their battles (maneuver, movement speed and shock would help reflect that)

https://en.wikipedia.org/wiki/Assassins

Lastly Sunni would focus on mercenaries (mercenary cost, mercenary discipline), diplomatic (diplomatic rep.), and cavalry (cavalry to infantry ratio, cavalry combat ability). The importance of cavalry in the pan turkic-mongol muslim world (much of the middle east, central asia, and india were ruled by turkic dynasties) cannot be overstated. Horses were also deeply important in Sub Saharan Sahel Africa as well (possibly allowing the raid function to Sunni as well). Much of this regions were also Sunni. As Sunni is the main stream of the muslim religion, nations that follow the Sunni Islam should have increased diplomatic rep. Lastly, mercenaries in the form of Mamluks (slave soldiers) and practice of devshirme (the kidnap, selling and training of christians into soldiers) were common practice.

https://en.wikipedia.org/wiki/Mamluk
https://en.wikipedia.org/wiki/Devshirme