I think a faction based on the Ottomans, like the Ormeli from the original mount and blade mod The Eagle and the Radiant Cross, is need for Nova Aetas. It would be provide real threat for the Mithridian Empire and the Sarranid Sultanate. I am going to use Ormeli as placeholder for now on. The Ormeli in the early game they start around the Hashalla area and are usually aggressive towards both the Mithridian and Sarranid, often launching Jihads against the Mithridians capital. Once they conqured the Mithridians and Sarranids, they would turn their focus on Rhodoks, Zendarr, Papal State and Swadia.
The Ormeli at the start of the game have 2 troop trees, the Ghazis who are the tribal irregular troops and Kapikulu also known as the Janissaries, with both troop trees using historical. Ghazis are recruited from Villages and Towns of high Muslim religious unity, they are mostly comprised of light infantry and archers and decent missile cavalry. The Kapikulu are the real powerhouses of the Ormeli and are the reason why the Ormeli can easily become the strongest faction in the early mid game. They are the strongest troops available to the Ormeli having access to strong archers, heavy infantrymen, heavy cavalry and musket-men being available whilst all other factions are still at feudal tech. To balance them out the only be recruited by Ormeli vassals and from either the Capital or from settlements of low religious unity and are fairly expensive. I have managed to make a troop tree for the Kapikulu. Feel free if you think it needs extending.