I appreciate this might be a little niche. However for the site I'm building it would be enormously helpful and there are plenty of other site genres out there which would benefit from this as well - essay sites, journalism sites, literary sites etc.
A word count option in articles.
When an article is posted the option to have a side bar appended to the layout with a word count showing, and even features such as "search by word count", could be really super useful in certain industries.