You can't demote a priest from Full Member status, but you can demote one. The ramifications of a priest abusing their powers for political purpose is typically much more severe in SA.
Yes, that's what I meant.
In any case, I'm no SA priest, the decision ain't mine to take. It still is an option, however.
Easiest way would probably be to take over the West Divide, give it to D'Hara, put ton of militia in BR, wait for it to bankrupt and for all militia to leave, then ask for D'Hara to invade and TO BR. Then D'Hara can give it all back. After all, Sevastian is threatening D'Haran ambassadors for no reason and inciting violence.