Since this control already supports drag and drop, why not implement item sorting using that same method, client side. On client side and server side, would be useful to have access to that reordered list of items so that it could be saved to a database.
Here is a live example of how a gallery of images could be reordered with a nice highlight effect after saving the new position.
Also, it would be very important to support responsive behavior and touch devices.
I believe this would be a step into perfection of this wonderful control.