Using "culture" in place of "religion" is good enough.
Whenever "religion" was used as a cause for war, it was simply to mask political gains for those waging it. Even the crusades were attempts to assert political influence or gain more secular titles. The average soldier might have been a zealot, but most kings simply wanted more power.
Religion is already assumed to be a piece of what makes up a faction's culture anyways. I say, leave it abstract and let the players assume whatever religion they want for a certain culture.
요약: 응 문화로 충분해~
문화 안에 종교도 넣어서 퉁치겠다는거구나
개소리를 길게도 써놨네