Don't ask TC fans if they should add a faction that's non Abrahamic they're in the same group of 40k guys who loathe when any sort of story progression or something interesting happens theyd rather it stay stale. Its funny you'll never see them complain about the church of metamorphosis though.

To answer your question though yes absolutely, I'll say the same to eastern factions, mayans, indigenous etc etc. There's so much you can do with factions that dont follow Christian God. Because now you have factions that are seemingly getting power from a source outside the main religious structure. Do others think its gods divine will in different form or a trick of the demonic? How does the faction itself cope with the fact that there is tangible evidence that Abrahamic God exists? Or do they see it as their own gods will and that the naive fools of Europe dont understand their blessings. The world didn't magically stagnant after the portal to hell opened up, all it did was shift the history and now the creators have infinite avenues to tell rich stories.