We already have those capabilities. My website has reposts on it. I just link to someone else's content from my Atom feed instead of something hosted on my own

We already have those capabilities. My website has reposts on it. I just link to someone else's content from my Atom feed instead of something hosted on my own site. Then I attach a https://validator.w3.org/feed/docs/atom.html#category https://validator.w3.org/feed/docs/atom.html#category node indicating that those are reposts.