I think it all depends on your client. I like the room within a room concept. If it were my home, it would be turned into a private office (where the kids can't get to it.). Or it could be a great nursery so that the baby is close, but in separate space that could still be viewed. On the other hand, it would make the Master Bedroom seem larger to have it just be open.

It really depends on your taste. There is no right or wrong answer. If you like it then go for it. There's no such thing as "too unique". Either way I'm sure it'd look nice.

Maybe the glass between the bedroom and sitting room should be operable doors, or folding Nana-wall style doors. This could give the best of both worlds. (but would increase cost a little)