With a POD after 100 CE, find a way for Persia to adopt Christianity but the Roman Empire doesn't adopt Christianity (it doesn't matter what religion the Romans have ITTL as long as they aren't Christian).
Bonus points if you could get this Christian Persia to be the "springboard" of the Christianization of large swathes of India and China as well.
Bonus points if you could get this Christian Persia to be the "springboard" of the Christianization of large swathes of India and China as well.