This suggestion is already half-implemented, (With many thanks to Friedman for doing so!) but the jobs not done until it's DONE. Right now, there are a lot of points in my stories where I'm collaborating with other authors on threads or branches that are unpublished yet, and it's maddening not being able to see anything in those branches except my own chapters! Sometimes I'll even add nearly blank chapters as sort of bookmarks if the thread gets particularly long. What I propose is that story Owners and Co-Owners be able to see ALL the chapters in a story on the story map from ALL users, not just those published or waiting for review and their own unpublished chapters...
It could lead to problems if inexperienced story owners/editors see a story draft by other authors. They could accidentally edit, publish or delete such chapter drafts. Of course, that can also happen if the story owner/editor reaches the chapter from a chapter answer, though I think that it is less likely to notice a chapter that way and the status "not published" is more prominent there. So maybe only allow it if the user chose that option in their setting or make it more obvious that it is another user's addition. If I remember correctly, it was possible to see all chapters on the story map when CHYOA launched and I could imagine that it was removed because of the FireFox bug which didn't show the label which made an unpublished chapter or chapter in review look like a published one. Though in general, I support that suggestion.
Whenever an owner reviews a not published chapter, you could have a note pop up that says "This chapter has not been submitted for publishing, and the author may still be editing it."