I don't think your solution works for this use case since what he wants is to save the "XML serialized" SVG element instead of a "JSON serialized" JavaScript o

I don't think your solution works for this use case since what he wants is to save the "XML serialized" SVG element instead of a "JSON serialized" JavaScript object. A simple d3.select('svg').node().outerHTML would do the trick. (You can use the same trick as in console-save to generate a download URL though.)