In the new "First questions" review queue there is an option to "Share feedback". The current choices are the "unclear" and "too broad" close reasons, but you can share these here without initiating the vote to close.
Is it possible the add the "problematic homework" explanation with a link to the FAQ?
Edit: This question incorrectly stated that the "opinion-based" share feedback option was already implemented, but it isn't. Is it possible to add that as well?