Rule based email template assignment to an email and sent and archive with ability to undo for 30 seconds via hitting the Cmd+option+Esc
Example: if email contains words "refund" allow the system to suggest to reply with the 1"refunded" template or 2"purchase not found" template and all I have to say is push cmd+1 or 2 to have the message replied to with that template and open the next msg.
That way I could use the number pad to answer emails with just cmd + 1,2,3,4, - and 0 being the default - of answering manually and command + shift + 1,2,3,4 to insert template but let me make a local override before sending.
That would allow me to answer emails 100 times faster.