It is incredibly rare for us to have a dedicated chat screen where all users are talking to each other. It would be much more practical to have a chat component. The interface would be identical to the chat screen, but it would function exactly like the comments component—Unique topic, sorting oldest to newest, etc.
Bonus for the chat component to also allow photos/files. I would say 75% of all my clients have asked for legit chat functionality. This would be the biggest win since Actions.