Before I say anything else, is there a specific place where people can submit proposals/suggestions? If not, one should be set up. And if so, the navigational structure should be improved because it's hard to find!
Upgrade to MediaWiki: "Save Draft" button beneath the edit box that saves the box's contents to a logged-in user's subpage: "User:Example/Article title". Far too many times I'm halfway through a massive edit and I have to go - there needs to be an easier and/or integrated way to save half-done work between sessions.
This automation of "in-progress" subpages will neatly streamline copyediting and extended work too.