1) When I founded a religion, people would join but not follow "holy edicts" so I'd excommunicate them. But nothing actually happens.
This is something I too have struggled with religion. On one hand, you are trying to expand and gather new members, and I'm more interested in OOC atmosphere/community than theological roleplay correctness, but on the other hand, enforcing the actual ideas you're trying to promote and being seen as fanatical for trying to be follow through on convictions.
There should be a large drop in honor/prestige & maybe affects on your region if you are thrown out of the church.
Added to my religious list. One day I'd like to make religious required to join on character creation and immigration, but there are other changes that much be done first. Once those occur, this would be an excellent complement.
2) Churches have their own hierarchy in real life. Why not match that with parishes, etc. that collect gold from the temples/peasants, so that you can increase your influence by getting more believers. Also perhaps some prestige bonuses in there as well, would be natural.
These, very roughly speaking, are those first changes required.
A few fame points might even be possible, I'd think - x thousand peasants under your benevolent wing
More changing the existing founding-religion fame to be more accessible to any priest and discourage religions being founded just to collect fame, and being dead meaningless shells.
3) A little far-out from how we actually play, but: make Gods "real". Like the Ancient Greeks, make the Gods actually influence things in the game.
I've been thinking of endorsing existing religious roleplay with Portal or other GM events.
Maybe Gods overall believers can be translated into some sort of strength score & they can influence the outcome of battles, or you can sacrifice to them to increase your performance; maybe they will help guide an assassin's hand...
Well, there is the Visit Temples feature that is affected by existing temples and which we could base some improvements on. And I do have regional buffs affected by religion in a branch I'll finish testing and send live sometime. But generally speaking, we're going to quickly hit the wall of Volunteer Time for as many good ideas as we can generate.
4) get rid of the rule where a religion dies when its last temple is destroyed. It should die naturally when no more temples & no more priests who might restart it with a new conversion of a lord, or building a new temple
This one I disagree on. For what its worth, the vast majority of religions are not destroyed by the last temple. They are destroyed by a priest elder character pausing and the religion collapsing before any others can step in. In the case of the last temple being destroyed, which I only know from recent experience of Sorachism being closed on the South Island, it gives 4 turns before its closed, in which a lord can build a new temple. In the case of no priest elders, as many turns as the highest level temple.
If a religion cannot sustain interest in itself to survive, it should not survive. I think we err on the side of too many religions, too many indian chiefs with their Awesome Theological Roleplay, and result in too many boring one priest religions that die; EC especially, other continents not so much. Religions should not be as small and numerous as realms. And yet at the same time, people fear secessions and want large realms with distant marches to war (if war). Bah.
I think Religions should not be given mechanic powers. SA was plenty powerful through influence alone with very few religion specific mechanics. In fact it got so powerful that things began to grow boring on Dwilight outside and inside the SA bloc until the ESA split.
We're well aware of the concerns of balance. I'm generally thinking of residual religious effects more than individual mechanical powers. But we do need to cleanup, fix, and tweak the existing mechanics that priests have. Religion should still be primarily an influence role, but there should be some mechanic shoreup to encourage religion being more important in a nobleman's life, not just his realm.
