Both a cross and a yamulke can both be accomodated as a religious accomodation with no concerns for safety or security. The head scarf, which completely covers everything other than the eyes, is a legitimate safety and security issue. I would think an employee would be similarly restricted from wearing a mask or a hood with sunglasses. This goes hand-in-hand with the Muslim women who want to get their drivers’ license and employee ID photos taken with the burkha on. These are forms of IDENTIFICATION, so it makes absolutely NO SENSE to take the photo unless you can clearly identify the employee.
The purpose of a uniform is “uniformity” of employees.
There are lots of examples where Christians have been forced to remove a tiny cross pin, cross necklace or even a Christian chastity ring. (Google “employee told to remove cross”)
So I don’t buy your comparison.