I use templates extensively! And I use Discourse Templates the same way I use Discourse Chat: alone, one-on-one, and in any possible group configuration! 
In each of those examples it sounds like how PMs work, which I think is great: the ability to add and remove users and groups…
Hmmm… maybe having options similar to how Discourse Docs sets categories and tags.
However, in addition to showing all template topics available based on category permissions in the template chooser, it also loads PM templates. So you would tag all your PM templates as needed, and would share them as a normal PM (users and groups).
