The correct answer here is that there are no other religions with such an extreme requirement in terms of headgear. If you’ve got the Sikhs covered (well, if you let them cover themselves as they please) then you’ve got no worries about other cases.
Gotcha, but I’m just pointing out it’s a court case waiting to happen especially since the Army allows Jews to wear their headgear...extreme or not, that’s the point and I can see it getting that far in today’s society. Put it this way, the Army will have to disallow all religious headgear or allow all. JMO.