Make it quicker and easier to heavily customise shortcut keys
We used to have this feature in Excel 2010 and they took it away. Yet it's still in Word. Why? Do you really hate Excel users that much?
Levi Bailey commented
Example: Allow us to drag buttons around the quick access toolbar and the ribbon, just like we can in the Windows taskbar. Also like the windows taskbar, having a "Lock the [quick access toolbar/ribbon]" option in the right-click menu would likely reduce issues people have with inadvertently dragging buttons around. I do realise that we can move these things around in the Customize Ribbon tab of the Excel Options dialogue box and am hoping for something quicker.