Is Kush religious though? If he's not, then it might not be an issue. I have a feeling the writers will just brush it under the carpet to avoid tackling any sensitive questions. EE has never done a good job of exploring religion and has a rather smug/dismissive attitude toward it.
Although if Kush is meant to be Iranian, then one would think the writers chose that nationality specifically because the majority of Iranians are Shia and knowing this would cause conflict with Shabnam's character. I just can't see the writers being able to sustain a whole storyline out of it though. Like I said, religion is not EE's strength.