If you feel the need to found another religion, I strongly urge you to make it an aggressively inclusive religion, politically speaking. Don't make it Yet Another State Religion that's just going to be treated as an extension of the realm...because that's what it is.
And if you make it a religion that's "primarily focused on Xavax-inspired lore", that's exactly what it's going to be seen as, and your potential follower base will never be larger than your realm (in fact, it will almost inevitably be smaller).
What BattleMaster needs isn't more religions. It's better religions—ones that can actually attract people to them by being interesting and non-realm-based. Only then will they be able to create conflict separate from realms.