I assumed that by "true neutral" you meant that it would turn anyone neutral. Are you saying you want it to be just another FoL alignment-wise? I'm not a fan of that. This is not a religion that tolerates evil, even if it is not fanatical about fighting evil either.
I do not like the idea of OO being removed. It could use some improvement though. Frankly I think that Mammon is important in all the evil religions (including AV, since desire for dark powers is still greed), but these religions are not the same thing.
I would like it if some religions moved you one towards good/evil instead of how it works now. The insanity of the Overlords religion seems more likely to draw you to true evil however, while the Empyrean is clearly more good than Runes (or than The Order really, although not as fanatically opposed to evil as food in FfH tends to mean).
I'm thinking it may be a good idea to add religious-specific events that let civs change their alignment rather than changing alignment automatically.
The big problem with adopting religions is that the AI's religious weightings are very low. They should be increased.
Really, the game needs to have a more dynamic tech weighting too. Alignment, Religion, leader, and civ should all have their own modifiers to tech weights. These would drive the AI towards the units/heroes/buildings/wonders/civics/religions/improvements that are the most thematic and powerful for the civ. I despise the current way of simply forcing a civ to research something if it can, which is why FoL and RoK are founded so soon by the Elves and Dwarves.