[member="Sarge Potteiger"] [member="Aaralyn Rekali"] [member="Sirella Valkner"]
I say it's up to the creator of the submission to regulate the use of his own stuff, and to report it when it's being used by someone without permission. I think Sarge will agree with me that we love those kind of reports. A submission owner saying "this dude doesn't have permission to use something I created" is SUPER easy to handle, because if the creator doesn't want them having it, it's pretty much open and shut case, Johnson.
I really don't think this is a widespread issue, if an issue at all, and don't wish to point our rules at fixing something that doesn't exist.
However, I see no problem with a "Characters Who Can Use This:" at the bottom of each template as optional, and can be updated via Submission Modification.