“But as long as teh restaurant keeps the halal rules, there is no reason it shouldn’t advertise as halal and have Muslim clientele.”
On paper, but sometimes it’s better for business for certain things to go without saying. If people can get up in arms over a storefront displaying “Happy Holidays,” then it’s not too much of a stretch to think advertising as Halal might turn some people off in regions where the religious Muslim population is known to be unfriendly towards the Jews.
Gadol: Halal is actually extremely meikel once the animal is shechted. They don’t avoid parts of the animal like us, or check for blemishes to my knowledge. So, I don’t think they would differentiate between Bet Yosef and Rema. In fact, I think they’re even OK with Hebrew Nationals, unlike the Hebrews (that’s how you know WE’RE the real chosen people).