I'm sure CMs employees love the fact that they are both off the rota every Sunday. I'm sure no one else they work with would like a weekend day to spend with their family.
IMO if you work shifts then you work shifts, you don't always have the weekend off as you accept it is part of shift work - I can't see many nurses, police officers, prison officers etc requesting a day every weekend off (my own husband included).
If you want the weekend off constantly you look for a job which offers that working pattern.