Having an additional picture in the picture button directly on video content (e.g. on hover) is such a convenient-to-use feature. Just like firefox and its derivates have it. A chromium-based example for this feature would be Vivaldi.
As pip already exists it’s probably not that hard to extend it by a feature that is similar to this request (to leave freedom to creativity how this will be solved, this request is like throwing a ball and seeing how it will be played with). In terms of improving user experience, I would love to see something like this (of course this is my humble opinion, but designing UI’s for 15+ years I feel the freedom to communicate that opinion.)
Kudos to the devs for all the work!