Something I find common to many RPGs is a definitive quasi-supernatural meta-history for the setting. Quite often it has vague parallels to the Judaeo-Christian myth, with a single god creating the world, then creating a host of lesser gods (or angels) to look after specific aspects of the world. The dominant race (or at least "the race of men") typically worships the great creator while other races worship the lesser gods.
In a postmodern age, some might say that this notion is inherently racist. It draws strong parallels to the Christian belief that there is no other correct worship than their own. It reeks of religious imperialism. It basically fits the general feel of most RPGs with their setting in a pseudo-Europe during a late dark age or early renaissance, but when RPGs strive for something a bit more exotic, it just doesn't feel right in my mind.
If I'm developing a setting with seven different core cultures, and seven different core races, I want there to be a few different creation myths. If there is a dominant "Church" culture then they would have a very specific idea about their theology and cosmology, if there are "Natives" then they would have developed their own religious beliefs independently, and it there is a "Cult" they might follow a specific heresy of their own that incorporates theological ideas from the main church while subverting such ideas to their own agenda. I'd imagine most other groups would be fairly agnostic about their religions, their beliefs don't define their lives, they're more focused on things like the physical world, wealth, and just surviving everyday...they might pay lip service to the other religions, but this isn't their life. Similarly, there could be members of the "Imperial/Colonial" forces who simply follo the faith of the church, and there might be some who follow the "old ways". Settlers might have a hybrid religion picking elements of native beliefs with the superstitions of the "church" culture.
I think this touches on a whole lot of new points to consider, certainly moving beyond the core structure of a Boffer LARP.