create-file-with-data should work with a text message as well
The manual states
--create-file-with-data=PATH
This option takes an SMS that has DATA (not TEXT)
and will create a local file described by PATH and
store the content of the SMS there.
It would be nice if this option worked on text messages just as well. It seems wise to inspect the contents of a message before manually deleting it. The only other way I see to do that from a CLI is to run MM in debug mode and search the log for it.