This is not the correct forum to argue who is and isn't christian.
I do hope nobody here is making this personal, if that's even what you mean. If at any point I say something that makes someone uncomfortable I sincerely apologize.
Not wishing to get too technical, but Mormonism isn't really a form of Christianity - since it is not a monotheistic religion (which despite the Trinity, Christianity is). For one thing, Jehovah (their God) just happens to be one of billions. In their theology, Jehovah's spirit spawn happen to inhabit this planet (having derived from Kobol).
The only similarities are the appropriate of the Christ figure.
In EU4 terms, if Mormonism was to exist, seeing as they were relatively intolerant times, they would have faced a massive amount of persecution and certainly wouldn't fall under the Protestant umbrella.
Judaism arguably wasn't even initially monotheistic either. It's right there in the Torah: idol worship, false gods, even a point where there's only one ragged old prophet of Yahweh left in Israel. The first commandment doesn't even sound monotheistic. So what?
Mormons were treated like absolute garbage in real history, so of course that would follow in the game. Drop an off-faith custom nation anywhere and people hate on them too, whether it's a Norse blob in Europe or a Shinto republic in Constantinople or whatever. No need to get creative here; opinion modifiers for different/heretic religion and CBs with certain ideas already exist.
As for arguing who is and isn't Christian, I would challenge anyone arguing that someone is NOT what they say that they are to ask themselves why. Whether it's a Mormon saying they are a Christian and you saying no you are not, or a person with a Y chromosome saying she's a woman and everyone and their mother linking a vanity fair article on social media to talk about trans issues, or anything in between. The burden absolutely falls on the person telling another person that they are not what they claim they are to prove it, definitively, with definitions and examples and whatever else. Until then, saying you aren't a Christian despite claiming to be because X feelings/beliefs is fallacious as an argument, and even if you CAN definitively prove it (doubtful or someone here would have) it's apparently not the forum for it, so I see no point to even go on with it. It's not like they're gonna add it like they did Judaism (which is Pagan, heh) anyway.
I suppose I'd have to see how new Protestant mechanics work before going into more than this, but, it would be AWESOME if it had an almost custom religion feel to it, where each protestant nation could choose to be the same as another (for great feels) or be unique, to simulate the many various protestant branches, complete with choices like being tolerance improving opinions or isolation to increase warring heretics, and protestant work ethic balanced with legitimacy issues and even tech issues, etc. This should, hypothetically, let someone create a Mormon religion, or Anabaptist or Scientologist or whatever you want to design and name, and be awesome. Probably a pipe dream though.
