Well read here:
http://en.wikipedia.org/wiki/East–West_Schism
In short there will be events to trigger the "flags" so Orthodox will become a religion and the Eastern provinces convert.
well im sorry if im rude but that has no logic at all since in the begining all the roman empire was orthodox what i just read only shows when the latins and so rome decided that it was going to be the head of all churches and started aplyng new fundamentals in the teaching of christianity the east and so traditional faitfull churches, didnt acept this so they splitt and the west was reffered to as catholics so if im right they should already be split in 2 catholics and orthodox and not all catholics. If you do want to reppresent faitfully the schism than you should make them all orthodox and after make flags to turn the west chatolic that's how it went historically!