At least one goal must reference a particular civ instead of all civs of that religion, because there has to be a way to determine the civ that actually wins the game.
I haven't played SoI so I don't have much input but aren't there a lot of civs right now that basically are reliant on founding religions or spreading them? Isn't that in a way a religious victory? It's a good suggestion I guess but it also seems like it would need a lot of work to function properly. Then again, I don't know much about the implications involved. MEH. :s
Civs with no state religion (egypt, babylon, greece, rome, maya, inca, aztec, etc) need a urv as well: heres what i propose:
URV1: ensure that no religions are present in any of your cities
URV2: ensure that at least half of the world's cities have no religion
URV3: have 10000 culture in one of your cities
*Ensure that all your cities don't have any religion.
Still impossible, as there's no way to prevent religion from spreading to a city without religion and no way to get rid of it once it's there.
Also, keeping a city without religion until Protestantism is founded is probably impossible for anyone except the native American civs (if they get lucky and Protestantism is founded early and Optics/Astronomy researched late).
Personally I wouldn't make URVs for civs without religion, because it is an unique religious victory and also pantheon URV isn't realistic for the later civs, but if Leoreth wants them, I guess we are going to get them.
Remeber the PERSECUTION PROJECT? It is still a thing that exists. It didn't stop existing or anything.