Why not just make them type the message out manually every single time? Why is it a good idea to offer options at all?
Yes, in situations where the message does not fit within a pre-defined list due to an unexpected event. Of course it should still have security mechanism's to ensure that the transmission is properly authorised.
The biggest threat is probably misuse by politicians rather than the poor clerk!
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.