WI: The Ottoman Empire converts to Christianity?

Well no, those areas were still massively Aramaic. There was a significant Arab presence though.

Anyway, to convert Seljuk to Christianity while making Osman a Turkish name, just have an Arab Christian priest or merchant named Uthman go to the Oghuz Turkic territories.

That's reasonable enough, I guess, though it still doesn't get over the obstacle of having the Turks settle Anatolia without going through Persia first.
 
Sticking close as possible to history: After the collapse of the Sultanate of Rum, a group of Christian Turks led by a man named Osman (maybe born to a Muslim father and a Christian mother?) carve out a territory for themselves. They prosper. Yadda Yadda, relatively good relations with the Byzantines and Latins, Yadda Yadda, they take over Anatolia.

Well, this scenario is very similar to what I've used in my own timeline... with some differences and a different context due to butterflies.
 
You'd probably have better luck having the Pechenegs or Cumans pull an Ottomans and establish an independent state in like Thrace, slowly cannibalizing the Eastern Roman Empire bit by bit.
 
I couldn't see many political situations arising where the Ottoman Empire would benefit from such a move,and even then I feel like the traditional sense of the Ottomwn dynasty would see them taking an alternate rout.
 
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