My experience says that when you copy a container all object inside are copyed too but ... they have the same id of the original container so any change in the object in the second container will be applyed to the first container.
So:
Copy the container, remove all the object inside, change id of the objects finally compose again the container.
I use 11.2 sr5. If you have a copy of the object outside the container and copy the cotainer it works. But if you don't have this copy it does not. Could you confirm me that in 11.2 sr8 you copy container contens whitout have a exteranl copy of the objcets ?
I have updated to 11.2 r8. If you copy containers among sheets in the same document it works. But unfortunately not it the destination is other document. it a step ahead but not the final solution.
