I'm glad you asked, because we already have the answer built in to Obian society: The Sacred Realm is a theocracy, therefore anyone is not a member of the church are likewise forbidden from holding office. That is, any office. No lordships, no marshalships, and certainly no ruling council seats. These knights are effectively second class citizens and will be treated accordingly. If the player(s) don't like being treated as such, then it is their choice to either join the temple or find some other place to call home.
We do not have the right to tell players how to play. Similarly, we are not obligated to make any special accommodations.
