I think it would be incredibly useful when adding a new user (let it be a home user or friend) to be able to have an option under user restrictions to select between local, remote, or both. So if you don’t want them using up ISP bandwidth, you can limit them to only being able to stream when they are on the same network.
So I guess it would be as simple as when they log in, the library/content only displays as available to them if they are local. If they are remote, the content can be greyed out or missing.
Just an idea 