There is a substantial difference between making major changes in a religion's doctrine or political structure from the top, and simply doing your level best as a priest to turn peasants away from that religion and close down its temples.
If your character does not believe in Sanguis Astroism as it is currently structured, then he should no longer be part of it. The only reason you have for remaining in it is so that you can reduce the number of people believing in it—an act that is obviously antithetical to the actual goals of any religion—without having to do the work of setting up a competing religion, or run the risk of being attacked by the peasants you're trying to convert to a competing religion.
I don't care if the religion in question is Sanguis Astroism, the Blood Cult, or Yet Another Pointless State Religion. No one gets to pretend to be a believer or priest of any religion just to deliberately reduce the religion's following. Damaging the religion politically out of ambition and attempts to take control of it, even to change its doctrine to something they know would be disliked by a majority of its current followers, are a completely different matter.
Every. Single. Faithful. has publicly opposed Alaster.
If the game won't handle schisms or give us tools to get rid of usurpers, then that's not the players' fault.
Enoch did not believe in SA. He was one of those, what do you call them again, spiritualists? He ran for leadership of SA, then put in the most hated heretic just to bring it down.
Enoch, Jonsu, Alaster took great power, without making any effort to improve the church, only to bring it down.
If you are going to tell me that that was more justified than a priest returning to the people he converted and telling them "you know what, the usurper in charge does not represent the teachings I told you", I call bull!@#$.
