V interesting thread..may I throw in a thought or two about the reduced Vr?
Using improved climb procedures, perhaps the 0-wind Vr may occur at the furthest point down the runway at which the climb gradient permits you to achieve the screen height, or meet other over-riding obstacle-clearance requirements?
Does it follow that with a tailwind, you might therefore need Vr to occur earlier along the runway for the same weight (a few knots less) to achieve the screen/obstacle clearance gradient required?
Or am I oversimplifyng things?