Is this a good idea? would we be hunted down for using actual religions in a game?
Religion is a pretty tough topic in certain parts of the world (US, middle east), so it might draw a lot of attention of all kinds there.
Since religious (and others, really) fundamentalists usually act irrational, there's no good way to predict what might happen.
Anyway, I suggest you watch these 2 videos to get a feeling on what's a good approach to the topic from a game design perspective: