I would love this feature! I currently have four sites in my multi-site, and all are related to the master site. Being able to duplicate pages between the master, and the multi-sites would be great, if for nothing else to put fresh content up when the other sites forget. When we duplicate pages currently, any dependent pages are not considered, generally it is just the content on that page that is needed.
If I was to replicate a group page, it would certainly need the dependent pages as well.
I don't have any opinion on multi-lingual, considering we have enough issues with English.