I think either a Chinese or a Sikh family would be interesting. They've never done the first one. Perhaps could slowly make Jo, the Chinese lady who works at Beale's chippy a regular and we see her family as well. As for a Sikh family, we've already had Asian Hindu (the Kapoors), Muslim (the Masoods and there was the Karims in the early days) and even Catholic (the Ferreiras) families.
The cast became its most diverse under DTC and it seems like most soaps have non-white or LGBT characters (even HO in the less than diverse has a regular black family). Of course I'm against tokenism just for the sake of box ticking, but if they work out as well as the Masoods, I'm totally fine with that. It's a question of finding the right talent.
Here's an interesting bit of info I found out about SOC: Apparently he cast Rakhee Thakrar (Shabnam) as a juror in an hour long special of The Archers which went out just a few days ago. I think this was an episode he did as outgoing editor of the radio show.