Been following this thread and playing around with the mod, following my unification of the Canadian Church I've had a few ideas I'd like to suggest; obviously, feel free to ignore them
1). The Confederated Church needs its own symbol, just for flavour if nothing else; having reformed it, the use of the Catholic cross felt underwhelming. I've looked around and I think this version of the cross, which incorporates Fleur-De-Lis, would work well

, particularly if the colour was switched to gold-it shows its still a Christian sect, but links in the Ursuline symbol
2). It may be impossible (I don't understand coding), but when the Rust Cult is reformed, the decadence mechanic could be modded in, as "Rust" or "Decay"; the faith could then be more focused on the "maintenance" of machines, rather than their falling apart
3). The Evangelical's, and by extension the Holy Columbian Confederacy, should be more prone to heresy than they are; rather than always developing into a massive blob across the lower half of the map. My suggestion would be to add a modifier of -50% moral authority labelled "Sola Scriptura", decreasing the MTTH for heresy events, and increasing the zealous and heretic penalties for Evangelicals and their heresies, as well as adding more heresies (Baptists, United Church, maybe even Lutheran?)-with a decision, perhaps by gaining a large amount of prestige and piety+High Moral Authority, that the Emperor can revoke Sola Scriptura, meaning only one definition of the faith is valid; perhaps even removing the council and instituting a singular High Priest; maybe shifting the name to Protestantism, if thats possible
4). Mending Schisms; despite that it'd be 1000 years after the schism between them, and the other faiths have changed dramatically as well, I think a Catholic ruler should be able to mend the different schisms between Catholicism and its offshoots-Anabaptist, Evangelical, Ursuline, Sagrado, even Falling Star-and yes that'd kill religious diversity, but it'd be so hard to do it should be more a bragging rights kind of thing to achieve; maybe make it so the Catholics have to hold all the other faiths holy sites and cost large amounts of piety to achieve (though if Sola Scripturia and the Unification of the Canadian Churches occur, the Evangelicals and Confederated faith should be immune to this)
5). More a question that anything else; is there a decent guide somewhere to history modding? Because if so, I'd be more than happy to help in fleshing out some of the Ursuline history, e.g. Agrippa the Maid and the Pope's around her; perhaps the Ursuline faith having been considered Catholic until Agrippa splits off from a corrupt church and takes over as the head in Quebec (as a side question, why is Detroit a Ursuline holy site? Just for competion against the Rust Cultists/Norse?)
Anyway, thank you for making this mod, I've been having a lot of fun with it; hope you find some of these ideas I've suggest interesting