If I am understanding your question correctly, this can be done. To make sure, I ran a test. Please tell me if these steps reflect your workflow:
1. Author A creates an article
2. Author A saves the article as a draft
3. Author A adds Author B as an author
4. Author A passes the article to Author B
5. Author B edits the article and adds a Future Publishing date
6. Author B saves the article
7. Author B posts as Author B
After I completed these steps, the article published on the future publishing date.
Are these similar to the steps that you are taking?