Lord Tirian said:
For my 4E points-of-light-inspired campaign, I'm leaning away from a pantheon, made up of a multitude of different faiths, but I'm going with a single, all-encompassing deity.
What I used in my D&D 3.5 campaign was basically a monotheist religion that had enough uncertainty built into it that it required faith.
There was a single outer plane populated by angels and saints, ascended mortals, devils and demons, and the souls of the dead. The outer plane was a sphere, with the Good pole separated from the Neutral middle by the river Lethe. Drink from it, lose your memories, and be reborn to a moral world. Separating the Evil pole from the Neutral middle was the river Styx, which was very difficult to cross (add ferrymen to taste). Souls of the dead wind up in the area that correspond to their alignment, thus it was very difficult for the Evil to get to the Lethe to reincarnate (they have to exist the Evil pole, cross the Styx, then trek across the Neutral region without being thrown back into the Evil region.
How the religion worked was that the Good outer plane beings believed and could sense a Good greater creator deity that transcended the Outer Plane and created and could control all of Creation. They believed that upon maximizing the number of Good souls in the Good part of the outer plane, they'd be able to transcend and join the Good creator deity is a sort of heaven. All of the direct intercession was carried out by saints (the clerics and paladins belonged to orders tied to saints) and angels, not the main deity. This level of indirection allowed religion to be a matter of faith because you basically need to trust that the single main deity exists and that the end game will results in the victory and transcendence of Good souls. Most of the Good angels and saints believed in the transcendent deity of Good but there could be some exceptions, allowing the possibility of Good but not monotheistic religions, if desired.
There were Neutral people (as well as some Good and Evil) who believed that ascending to the outer plane was a stepping stone on a path to perfection that would eventually allow them to transcend the outer plane or create their own worlds. There was another variant that was closer to ancestor worship. This was intended to have a bit of a Asian flavor to, with respect to reincarnation and perfection and ancestor spirits, as well as some other inspirations.
The Evil devils and demons argued that all of this was nonsense and all that they knew was all that their was and there was no greater purpose to existing that dominating and using what's known to exist. Evil in my setting was often similar to malicious psychopathy so the "Why?" to it was that Evil people enjoyed cruelty and hurting or killing others. They didn't care about any bigger moral questions.
Druids followed yet another faith. Each world had a spirit and it was the "spirit of the world" that druids served, thus when the died, they'd reincarnate onto the world that they served. Their interests were about the health of the world rather than any sort of transcendent morality, thus there could be Evil druids as well as Good druids. All ultimately served the maintenance and balance of their world.
The goal was that everyone could believe that they were right and it ultimately came down to a matter of faith. Do you believe in the transcendent Good creator deity that has granted souls free will so that they could choose to be Good and ultimately transcend creation to join the presence of that deity in heaven (there was a bit more to the cosmology that that, but that was the core)? Do you believe that the pragmatism of individual achievement and perfection will make one a deity or serving ancestors who have become like deities? Do you believe it's all about grabbing what you can and serving your dark desires? Or is your immediate focus the health and well being of your own world and nature? That all had an outer plane source of power and intercession didn't really answer the question of who was right.
Maybe not what you are looking for since it's less clear and certain than your ideas but I found that it worked out pretty well.