I hope that By God Alone has content for specific, real-world heresies that emerged during the time period (especially the Hussites!)
The lack of things like the Albigensian Crusade or Hussite Wars has always felt really disappointing to me, and ties into a larger problem I've had with CK3 for a while; there aren't enough new scenarios to keep things fresh after game start! Frankokratia was a cool addition, but we need more of that stuff, and the heresies and rites system being added in By God Alone could be the perfect medium for them.
These two events could be great late game Situations to shake up your realm, or spice up a campaign. Like the Albigensian Crusade could be a cool opportunity for minor dynasties and houses to gain land and power in France, shaking up the balance of power within the realm.
And to be clear, when I say that I want content for these guys, I don't just mean an event that says "A historical character named Jan Hus has spawned in your realm. Do you want him to become your courtier?". I want event chains and situations that could either rapidly spiral out of control or be the ground that I build the next chapter of my campaign on.