Target the zealots, absolutely! But limiting where someone could wear the burqa is not the same as eliminating its use. Just as prohibiting where someone is permitted to smoke does not prevent them from smoking in private, or in acceptable public areas. Both issues are involved with public safety.
Along these lines, I wonder what would happen if a store owner refused admittance to anyone who refused to show his, or her, face to a security camera? I imagine it would cut down on robberies, if nothing else. And would showing her face to a camera violate the Muslim proscriptions? After all, she wouldn't be directly displaying her face for all to see.