Thank you all for your replies. Here is more sketching:
The feature of restricting the temples to rural regions is a risky one, that I grant. It is one of those things where you tied your hand behind your back to make the fight more challenging. I believe limitations are necessary in order to carve out some personality for a religion. But it is a gain if at the end it makes people interested in the religion. The feature also aims at a situation where the rural lands are more or less dominated with the ancestral worship, but the cities and towns have one or another faith in them. The AFA could not care less what the peasants in the cities worship, since they are the ones consuming the food and not the ones who help bring about the gift of the ancestors.
The feature might also result in a deeper divide between cities and rural lands, if the rural lords would tend to have one faith and the urban lords another. AFA would also see it more honorable to tend a rural region than a city, which might swim against the main current of the game. The faith would strive towards total control of all the rural lands on the continent, a goal which would probably never be achieved, but those are the best kind of goals anyway. Since food is a holy matter to the faith and an absolutely vital one to the realms as well, this would be where the faith might gain some leverage even if it would never control the cities. On the other hand, the faith would see it as a sacred duty of the rural lords to tend their regions well as to gain more of the blessing of the ancestors, so the realms would also benefit from this dedication. Hopefully interesting stories would be cooked up from these tensions.
Apart from the focus on food and the respect for the ancestors, AFA would have no other imposed values. The values the characters followed would be based on the saint or deity of their choosing, all conveniently located within the same faith. If there were a lack of a certain type of saint, all it takes to wait for someone to die and then begin to emphasize those character traits of the deceased noble that the player finds interesting and try to start a cult around that. Of course those interpretations might be contested, especially by those who actually knew the deceased, so conflicts such as this one would be commonplace, and potential for schisms would be readily available. AFA would leave it up to the lords to choose which sects to support, and would only insist the temples in rural lands to be left unharmed.
Another feature would be the rise of saints to deities. An order of a certain saint would after a time begin to accumulate legends, both of what the saint did when alive on the earth and what he has done in the otherworld. The otherworld can be seen in dreams, and a member of a sect may introduce a dream he has had to the other followers and if it sticks, it becomes more or less codified lore. A cunning banker saint might, for example, trick another saint (or even a deity!) by making an appealing bargain that the other party later regrets. When enough otherworldly lore is gained (and a sufficient number of followers), the saint is raised to a deity (and is given a new name). Then the leader of that particular cult is given elder status in AFA.
The main point here is to create a faith with very little forced dogma. Instead AFA would provide the framework into which the players could create all sorts of sects and cults, try to gain a following and then hammer their ideologies to the pantheon of the faith. Theology would become more or less a shouting match and what is valuable, just and right would be chosen by the participants, not the elders (the exception being some sort of ancestral reverence and food matters).
Where are you planning on founding it?
My character is located in Luria, so there. On the other hand, Niselur might be in a need of a new religion just about these times, so if someone over there finds this concept useful, it could be founded there as well by someone else. I would not mind.
The main point to keep in mind with this concept is that it is not a power trip for the founder, as he is more or less impartial with the saints and deities and has more of an administrative and perhaps a mediating role. I myself would found it on the spot if I did not already have a character concept that I would really like to try out. Now I am undecided. I might do it if there is definite interest to it.
I could see the flow of the seasons having a special spiritual role here too.
Yes, the cycle of seasons is important to the harvest, so specific seasons would focus on different themes. Winter, for example, would be the time of the wrath of the ancestors (risk of starvation, other inconveniences) and a time for reflections of the self and communities.
Temples in rural regions are a pain to finance and maintain...
I really like this self-limiting feature, so I would be very reluctant to let it go. It cuts straight to the core of the faith, with a touch of "live and let live" attitude. It is a feature that makes absolutely no sense in the powergamer's world, so those types would shy away from it. But if it is a feature that makes the faith utterly ineffective for gaining control of even the rural lands, then it must be reconsidered. A watered down version could exclude the cities and still get some of the tensions mentioned. By the way, badlands and mountains are also left out.
