Yeah, the Orthodox connections look a bit too tenuous to be that viable. I was always under the impression that the Anglo-Saxon Church was more like a more developed version of the early medieval "national churches" which existed prior to the expansion of Papal authority in the 11th century - which aren't really possible to model in the game.
Also, events allowing you to choose your religion are quite complex and tricky, given the way the CK event system works!
Also, events allowing you to choose your religion are quite complex and tricky, given the way the CK event system works!