It would be nice to eventually have a way of seeing a diff between the current WIP draft in the composer and the live version of the post you’re editing.
Upon clicking this option/button/link, a modal would appear, possibly reusing in some way the current editions diff view, and show the diff between the composer’s version and the one the post is at.
It could be implemented as an option inside the “gear” button dropdown. All of its options are content editing actions, but I believe it wouldn’t be that out of place. In fact, I can’t really think of a better place to put it right now.
(Would it be compare against? instead of to/with noticed afterwards. Sorry for my English, trying my best :S)
I know this is probably plugin territory, but fingers crossed 
!