While I agree that the holding of Richmond at all costs, (i.e., the cost of the war), was fatal, I am not sure that abandoning Richmond was a viable option.
Richmond was the site of several ironworks, foundries, and munitions plants. I am not sure that the South had the wherewithal to pick up and move that manufacturing the way that Soviet Russia and Nazi Germany actually did during WWII. Perhaps a relocation to Birmingham (or, perhaps, Athens) might have worked had it begun in 1861, but at that time, the South looked as though it would win on the field. By 1863, that sort of movement would have been much more difficult, and once Sherman reached Georgia, it was too late to mean anything.