It would be nice to be able to reorder legend items using arcpy based on an index position within the legend.
Currently there is no intuitive way to reorder legend items in arcpy. You can insert items in respect to a reference layer, with LegendElement.autoAdd = True but if the legend has been manually reordered you may get unexpected results.
If each legend item had a corresponding index value and could be reordered based on its index, this would open up lots of possibilities for automating legend generation/updating, which I have had several requests for from members of our GIS Department. The current functions allows for some functionality they request but its not quite enough.