I don't see a higher V1 as any problem - it's an energy consideration. Your tables say you can accelerate/stop at 53T, so it is obvious you can comfortably do so at 48T. Same thrust, lower mass = V1 in less distance from brakes release. Max brakes at V1 (53T) with lighter a/c = less energy to dissipate in the RTO = shorter stopping distance.
My concern would be Vr and V2. Both are a function of TOW. Still, I suppose it is in the right (higher) direction given that V2 is almost invariably (on the jets I know) on the backside of the drag curve.
My airline uses the V speeds for the prevailing mass and temp, and the thrust for the assumed temp.