Hi, Jeff. I was once an instructional technology professor in colleges of education. In my last gig, I taught my classes with Discourse (which is part of why I now make my living with Discourse).
I organized assignments (or quests) in read-only categories and instructed students to reply-as-linked-topic (now on the link icon below a post) and put their post into the category for their class with a particular tag for that assignment. This made it easy for students to comment on each others work and for me to see whether students had done the work. I would 
their topic if they had completed the assignment, and wrote a script that would see that students had done the assignment and gave different grades if I had liked it and if other students had. It’s probably not helpful, but you can have it.
Having the assignments in their own categories made it easy to re-run a course and to use an assignment in multiple courses. The other cool thing is that when it was obvious that an assignment was badly worded or otherwise needed changing, I could change it immediately, making life better for the slackers who did the work late, and meaning that all those changes to assignments that I might otherwise have intended to do before next semester were, in fact, done.
You can see a syllabus for the last class I taught and this one too. This also worked really well, since the assignments were separate from the course, there wasn’t the copy-the-old-course-to-the-new-one at the start of each semester. All that was needed was to copy the syllabus and change the dates on it.
My courses were all (and remained for a time) public. Changing that is just a matter of changing the permissions on the categories, though. I think that I just put a link to the course in the school’s LMS to get people to sign up. You could use groups to invite students to the course and control access.