For all the talk about "race gating", I wonder if religion gating could be on the table? Being a devout Andrastian, would Cassandra be open to forming a romantic entanglement with an atheist Inquisitor? Agnostic? Someone who follows the Qun?
The race-gating seems to mostly be an issue of cinematics budget. I doubt the writers are just adding in more restrictions for the hell of it.
That said, if you're constantly disagreeing with Cass on issues of religion, I expect it will be treated as any other disagreement in the game--possibly lowering her approval, which could indeed lock you out of a romance with her depending on how romance and approval are actually linked this time.
That was a convoluted sentence, I apologize. 