As an alternative, is it possible for instructors to import content from Public Courses (into their own) without being on the roster for the source course?
Since the course is public, the source code would also be visible, but I doubt this would be a very user friendly way for others to get that content into their course.
What does seem like a user friendly way to do this however is to upload the public course to Canvas Commons shared with the Shared With setting set to "Public." This would allow anyone with access to Canvas Commons to create their own copy of this content and use it however they see fit. Some relevant guides: