Fixing Byzantium or "How I stole your Holy City".

The first holy city Byzantium conquers transfers that religion from that city to Constantinople, making it that cities Holy City.

For example, let's say Egypt founded Judaism. Theodora could go over there, smash thebes and now Constantinople is the Holy City for Judaism, allowing Theodora to rework the beliefs of that faith. Egypt (and only Egypt) could attempt to take it back and Constantinople would not be able to found its own religion. They could only do this with a single religion.

In essence Constantinople would have a HUGE interest in conquering Holy Cities as an alternative means to founding their own.

I assume you also mean for founder beliefs to transfer to the Byzantines?

While the idea sounds rather cool in theory, it's about as situational as your typical achievement. Too situational, really.

I really don't know what's the big deal here.

In BNW, you can get a guaranteed religion if you focus on expansion and early Piety->Organized Religion. Research Philosophy early and we're talking about 5 faith per city, excluding pantheons and natural wonders.

Also, some of those reformation beliefs like Evangelism make it much easier to spread your religion via (even cheaper) missionaries. 160 faith per missionary. With Mosque of Djenne, 3 spreads and the ability to erode foreign religions from cities!!!

I mean, what else do you need to play a succesful religious game. Take two founder beliefs and convert your whole continent. You even have a decent chance of converting the rest of the world after Astronomy. Just prebuild around 5 missionaries and bomb a whole coastline.

Again, Evangelism turns missionaries into mini-prophets.

Byzantine needs fixing?

It would be nice if they just reworked them all together around some theme of having the best city in the world or something.