To add some more body parts to this Frankenstein-thing, you can take the content-reloading parts of App::Mojo::AssetReloader to broadcast any change to all connected clients. That way, multiple sessions can edit the content at the same time, with hilarious results. Ideally, you then transfer any change immediately (or as soon as it is somewhat valid HTML) to reduce the amount of edit conflicts.

Converting this to a real multiplayer editor which shows the multiple insertion points is left as another exercise.