testsuncle how would that work exactly?
You mean not specify any recipients but manually send the link to select users?
That sounds out of scope for this extension since the whole recipient and authorization system wouldn't be used. It shouldn't be too difficult to make a special discussion type appear in the visibility scope but not the index endpoint for users who aren't authors in a new extension.
One problem is that with the default discussion slugger, IDs are predictable so a different slugger would have to be used. Even the ID system would have to be changed because you can read/post to discussions using the API with just the ID without any need for the slug.
Other option would be to include a secret token in the URL but that sounds way more complicated than unguessable IDs coupled with native permissions.