You're conflating two different issues. My original suggestion was a mechanism to prevent the clerk from accidentally sending the wrong message. Typing out the entirety of the message hopefully would force them to realize what they're sending.

Allowing a separate option for a clerk, maybe with confirmation from a supervisor or other clerk, to send an arbitrary message (with a separate approval chain) would be useful as well. In the Hawaii situation not having that option likely delayed sending out the retraction as they didn't have a built in.