This 100 tonne error is regularly made by aircrew in all sorts of airlines. Mortals only get to hear about the incidents where there is some noise attached. What is clear is that no airline or manufacturer appears to have bullet proof method of prevention. A manually (yes, in this day and age) calculated speed (V2 or Vfs etc.) guess based on estimated load, DOW and fuel compared with the figures generated by the loadsheet might be the way forward. More silicon is probably not a good idea because it may use the use the same rubbish as input.