So this is my idea for the actual mechanics for sects and schisms:
Allow a sect to be created by any priest of the religion (ideally requiring said priest to hold a region with a temple in it). It creates a sub-religion that they are the head of with it's own rank structure which is in addition to the church ranks (but not modifiable by the church elders). Add to "religion" messaging tab "everyone/some people in your sect" (and the ranks in the sect would show in the message signature here). Once a sect exists it can be joined from any temple of the religion.
Sect structure would be the same as religion structure including elders, full members and regular members. Elders in the sect need not be elders in the primary religion. If the leader of a sect leaves, then the sect the is disbanded and all members lose membership in the sect.
The head of a sect has the power to "declare schism" (which will also occur automatically if the head of the sect leaves or is removed from the church) which makes him the head of a new religion. When a schism is declared, all temples of the primary religion in regions belonging to members of the sect are converted to the new religion but the peasants are not (this will take time and effort from priest actions and temple influence). At that point the sect becomes its own religion with all the corresponding mechanics.
It seems like a lot of work to me but I don't know that there can be a "quick and dirty" solution other than implementing temple re-dedication.
