First of all I´m not a B 737 pilot but MD 80. Our company SOP call for V speeds according ATOW.
But I do change that criterium ocasionally.
Let´s figure out we are taking off in a 12.000 feet runway, for enviromental conditions our RTOW is MTOW 160.000 lbs and corresponding V1 152 Kts, VR 157 Kts.
If the ATOW is just 110.000 lbs and V1 112 KTS, VR 115KTS, I always increased V1 to equalls VR. ASD will increase but I´m quiet sure will be lower than ASDA cause we are allowed to perform a RTO with 152 Kts and 160.000 lbs.
I think is easier and safer to remain in ground until VR when taking off with such a low weight.
I think it would be unsafe, not only because performance and controlability but also regarding legal matters, to increase all speeds as we were taking off with the MTOW or RTOW.