Maths and Physics (same thing really)
Our 747 freighters had a weight readout but, whilst the B744 was OK, the old B747 system was considered too expensive to maintain and was disconnected.
the possibility of implementing a line check speed
I understand the V Force used that system. I wonder if it would be workable with the civil airline complication of variable thrust? Whilst I guess the speed could be tabulated or otherwise calculated would errors result in unnecessary aborts?