From my understanding, the Assumed Temp method is to save engine life. The V speeds are directly for the aircrafts performance at its actual weight. Ok, I see the safe arguments of an earlier V1, but why would you be using higher VR and V2 speeds than normal? You increase your ground roll. And effectively will be degrading your initial climb profile. ie, best gradient climb profile is at V2+20 (for Actual weight) If you start of at an abnormally higher V2, then your V2+20 will be at a higher than normal speed, which will then not be your best climb gradient speed but instead reduce the obstacle clearance angle.