One thing I would like to see out of this project is a better version control system for prose. Git is great for code, but it's not at all any good for editing text.
It's the diff-viewing infrastructure that needs to be completely replaced for prose.
I think you're right: if the diff-viewing infrastructure was abstracted (plugin?) it could do this and more (eg word-diff-by-paragraph, image-diff).
Harpjs is two steps ahead on this one.