My idea is to add more functionality to the scheduling of posts. I have a multi-author blog and I only run one post a day, so at time I have a couple of weeks of posts built up to run, and it would be nice in the scheduling interface to have a calendar that shows you what dates you already have scheduled, and which ones are open. Even better, show the number of posts that are scheduled for each day so I can see if I’ve double-booked (it has happened).
As part of cleaning up the scheduling interface, the current list of posts can get confusing when you have a couple of weeks scheduled out. Not sure how to fix this, but I think a graphic designer would have some ideas for making this more visually intuitive.