How would you do this?
People of other faiths are allowed to wear their religious clothing (our priest down the road wears what is, in effect, a long dress), Sikhs can wear their turbans (and not crash helmets) and carry their ceremonial items, Jews wear the Kippah - but none of these cover the face. Would you say that a desert Arab in traditional costume in London couldn't wear a shemagh, either?
I'm not anti the principle of being able to identify everyone, just asking how it would be implemented.