A cool idea, yea, but it would indeed be quite easy to snipe an entire victory without actually contributing anything to it. Imagine: your civ neighbour spends the entire game working really hard on religion, spreading it to all corners of the world. Meanwhile, you don't bother your neighbour, nor try to make your own religion. Perhaps you just passively gather some faith along the way. Eventually, your neighbour is just about to win via religious victory, then you declare war and capture their holy city, and end up winning as a result with very minimal effort toward that victory. Also, what happens if you have your own religion, but then capture an enemy holy city? Do you now have two religions under your name? Does one of those religions need to become dominant over the other in order for you to win, or do all other civs just have to have either of your religions be dominant among them? At first, I thought this would have the same problem as the other idea, where you could just piggyback off of others without doing much work of your own. But, if you create your own religion split, you'd have to put in effort to make sure your religion actually takes hold. This idea does pose a whole new problem, though, which is that it'd be quite a bit more difficult for other civs to win a religious victory, because if their religion was dominant in all of your cities, you could just split it off into a new one and they wouldn't be able to win because your cities would no longer be following their religion. Unless this split religion can still contribute to the original founder's religious victory (so that splitting a religion can't be used to merely delay an enemy's victory), as well as contributing to the splitter's own religious victory, in which case the splitter would have to make their version more potent than the original in order to win. Sounds fun, but really complicated. In the end, I'd certainly like to see some way to win a religious victory even if you miss out on a Great Prophet. It would help civs like Spain or Georgia which are more geared toward religious victories, but have no solid way to guarantee themselves a chance at a Great Prophet. One could argue that since you weren't quick enough to get one, then tough luck, and you should deal with it... but I don't find it at all to be a good thing that a civ can put in lots of effort toward the path to a victory and suddenly be shut out from getting it, making their entire early-game efforts fruitless. After all, no other victory functions at all like that.