The word "draft" is probably inappropriate here, but then again so is the word "template". Both have specific meanings in Lotus Notes that aren't what you really want. Users can delete drafts, and templates are an entirely different thing. So let's just call it a boilerplate message.
I would recomemnd creating a special mail database (NSF file) on the Domino server, which will just serve as a repository for your boilerplate. You can create a folder in that mail database called "Boilerplates". Using Domino Designer you can modify that folder's design so that the Subject column is the first column in the view, and it is sorted.
Once you have that done and you have created some boilerplates and saved them in the folder, you can use VBA to do a NotesSession.getDatabase call, NotesDatabase.getView call (this is used for folders as well as views), and then use NotesView.getDocumentByKey() to retrieve a specific boilerplate by the Subject you have assigned to it. Note that you do not have to copy this document to the user's mail database in order to mail it.