There is no standard option to do what you want, but I guess it is possible to edit the NAML to add the option you want.
However, why not just use Option 2 (Delete post and replies) and keep a file containing the content of your "Instruction" mail and paste it into a new message when you need it. It would only take a couple of keystrokes and about three clicks!
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.