I've been searching for a kettle that is wider than the standard 5" or so.
If you wanted to increase the efficiency, It seems to me that the width would mean no flame spill over, so neoprene/carbon felt or reflextic could be cut to lay over the top to keep the heat in.
If you wanted to lighten it, you could use 2 fishing leads instead of the bails, or titanium bike spokes/wire.
If you wanted to simplify/lighten it, you could weld a piece of aluminum in place of the lid. I have a Swiss kitchen kettle from the 50's that only has a hole for the spout. very slick design