"Where shall we go to church this week. Honey?"
I suppose it could work out. Friday, one could go to the mosque, Saturday to the synagogue, early Sunday morning to Mass, late Sunday morning to Baptist service (with dinner on the grounds afterwards. You know how much Baptists like to fellowship!). Everybody's happy!
Seriously, though. My main concern would be in regards to children. I would think that a child would experience confusion at one point if they are always shuttled around to different religious meetings. While I'm sure the parents may think that they are exposing their children to some kind of religious training and that in time they will have the freedom to choose which one to go to (or none, for that matter), they better be prepared for a lot of questions. Plus, I would think that it would put a lot of pressure on them to choose between their father's religion and their mother's religious. Surely, they wouldn't want to offend one or the other.