Well, post Edit, we have that shiny nice notification template lying around. "This entry has been reviewed and slated for editing" etc. Why not once an article hits -5 drop that onto the discussion page, minus the time limit and with a notification that at -8 the article will be deleted, and give the author one last chance at redemption?
standardising the procedure a bit more to give the authors a definate idea of which articles need help might work better than just a vote based system, since without checking the module itself there's really no way to spot that your stuff's been downvoted unless it hits a certain level, by which point it's often irredeemable. It'll also give the butthurt less of a leg to stand on while whining, since they were officially warned.
Something like this
This entry has been reviewed and slated for editing. If you are the original author, please review this entry and comments, and see what changes could be made. Other users may edit ONLY:
1.If the original author cannot be found/contacted
2.If the original author gives permission
Should this entry's ranking in the voting module fall below -8, it will be deleted immediately. Please rewrite accordingly, and PM downvoters for further review.