>>646840
Whatever I would do, under no circumstances would I have deities gain power from faith or pop into existence/change their attributes because people believed. That's just about the worst meme appearing in fantasy worldbuilding nowadays, and it hasn't been fresh or edgy in a long time.
An idea I like for a fantasy RPG is that gods are entities that come from somewhere and demand to be worshiped.
For example, the god of a primitive tribe might be huge man-eating giant snake. A small country of farmers might worship a spirit being that casts arcane spells to make crops grow if you flatter her. The PCs might well end up fighting with and killing either or both gods and taking their stuff depending on how things go, and the worshipers might even approve of it.
I wouldn't have D&D's system that divides between arcane and divine magic, or at least I would have the divine category be the domain of the real God and beyond normal rules involving statistics and die rolls. There would be no gods granting spells to their clerics, D&D style. Though, certain gods might teach their followers rare spells, and certain other gods who have the special ability might possess their followers and have them use powers they wouldn't normally have.
In general I wouldn't get too attached to the D&D way of doing things, which is a weird Christian/LARPagan/postmodern/gaming legacy mixture with little real thought put into the overall design and the meaning of it all.