Pretty bad choice if they have to choose between being assaulted in Poland and breaking one of the most important tenets of their religion
It you're referring to niqab, it is not required (it is in fact prohibited during the hajj).
If you're referring to turbans and if they are one of the most important tenets of Sikhism (how odd), then weighing the benefits of following the religion and following employment opportunities is a legtimate trade off.
wearing cross as a sign of religiousity is a quite new "invention
Yeah, I have no problem with making Christians concealing the cross while performing a civil service job in a secular state (or private employers requiring them to be hidden).
The wonderful thing about multiculturalism is that you end up with least-common-denomiator results that please no one.....