I have made some changes on my nop (but it is 3.6) and think these changes would be useful to others if they were added.
1. Having to scroll all the way to the top of edit pages to get to the save button. This is annoying if I am making lots of edits. One solution would be to add a "top" link that stays on the display bottom. I took a different approach and once I scroll down on the product editor page more than a 50px, the top buttons all become fixed to the display top, so they are always in my view.
2. List pages. I dislike having to click on "edit" in the far right of every row. I adjusted my products list so that the entire row is hot and the edit link column is not there. I find it easier and friendlier to simply click the row to edit. If the concern is that people tend to click in error, make it a double click to edit.
3. Ability to copy shipping address quickly. On my orders shipping tab I added a link button to copy the address. It puts the full shipping address in my clipboard for me and if that fails it will unhide a hidden textarea with the full address in it so I can manually copy it.
Just my thoughts to make the admin side friendlier and easier to use.