Hm. Maybe a game where instead of playing a nation, you are playing a religious leader. Like, have a game based inEurope, but ITTL instead of Nicene Christianity basically being a massive juggernaught that curbstomps most heresies, Rome is an absolute cesspool of different Christian ideologies, and thus you have to guide your way through the early years of Christianity (Ecumenical councils, foreign invasions) from maybe 33ad to either 1054 (the first real split between Nicene Christian sects) or 1517 (when the Protestant Reformation starts and instead of there just being one kind of new heresy that conveniently blobs around an area, there is an absolute flourishing of Protestant sects that would be difficult and arbitrary to display in game)