I think somewhere between Roads to Power and the Wandering Nobles event pack, more opportunities were introduced for strong republics to rise to power. While I was messing around in the frozen wasteland of Sibirya, Germany somehow established itself as a Most Serene Republic and has been going strong for many generations. I just popped over to check on them and discovered that their current elected leader is both a nun and a Conqueror. She looks pretty badass with that sword.
That is a very very interesting timeline indeed! I think in CK2 it could happen as well, but usually not over many generations. A Republican Nun is... An interesting choice for a historical simulator, to say the least.