I would like to see a Send Later functionality as some email clients have (like Thunderbird’s add on “Send Later”: https://addons.thunderbird.net/en-US/thunderbird/addon/send-later-3/).
How it may work: Set a date/time or amount of minutes/hours from now when creating an answer/new message.
If a new message comes in between setting the answer and the time it should be sent, probably sending the message should be paused and the agent should be informed about it.
There may be many reasons for not sending an answer right now when it was typed. I our case it is most often that people work at night/sundays but don’t want the customer to see this. So setting a date/time when the email should really be sent would be great.