To be meaningful, timing to V1 would involve a number of factors as we know and, as has been pointed out, would require more accurate weight information than the industry, including the regulators, seem to be presently satisfied with.
The travelling public are lucky that development of this "satisfaction" has coincided with engines designed for failures > 1 x10^9 flying hours. Or perhaps not luck at all; maybe it's because engines are so reliable that this relaxed and comfortable attitude with aircraft weights has become normal.