So another option (as suggested by @ben.megson in Realtime: Auto-save original document vs. a draft), is to always ask the current editor(s) if they’re ok that another user edits with them concurrently.
In a similar vein, I’m not a massive fan of everyone being able to join the live session (I believe this is the intent…). It would be better if someone who is part of the edit was required to accept participation of others.
This would solve the issue of CR mentioned above and you wouldn’t need to “Edit as CR”. You could just edit and if someone wants to join but you’re not planning to work with someone on your upcoming CR you’d refuse (would be nice to have a text message to explain why you’re refusing).