In contemplating the set-up I'm imagining for my campaign setting, it occurs to me that Jeff's Threefold Apocalyptic Alignment System is the closest to what I want to do. As I envisage it, all the gods -- even the evil ones -- are Lawful, because they stand on the side of continued existence of the universe, even if they differ on just what they'd do with the portion of the universe over which they have dominion. Chaos represents those who would destroy the universe, such as the demons and those who serve them. Neutrality is for those who wish neither the outright destruction of the universe nor attempts to master it, believing instead that reality (i.e. Nature) has its own logic that is aloof from the plans of both mortal and god alike.
(As an aside, I should note that D&D's devils, which I plan to use in some form, are solidly on the side of Law, being fallen servants of the gods who wish to rule the universe under their iron fists, unlike demons, who, through various means, both subtle and explicit, wish to destroy the very fabric of reality and cast the universe into the Abyss from whence they come)