Funny and interesting. Did you know that firepad.io is a rich-text OT text editor with timestamps? I think it's just what you need. You get a real-time collaborative text editor with a fully featured toolbar, and the exact history you need to replay.

Actually, Firepad does replay the history to display the current version on load (though it also has some snapshotting system to restart faster, but snapshots do not erase the history, they are kept in another location).