Ouch, why give the holes in the Swiss cheese more chances - the amount of ZFW changes over 4000 kg`s are not that infrequent to be ignored ie: sorted out on the way to the runway.
1. On Airbus FBW once the engines are started you can no longer enter the ZFW as a ZFW but must enter the weight as a Gross weight on a different page which the a/c will then work backwards to a ZFW - so a different page with a different input means a non standard way - anything thats non standard needs more attention.
2. Your paper flightplan generated on the ground by a ground based computer becomes less and less relevant as the ZFW changes - when do you ask for a new one. 4000 Kg seems to work for the 340.
3. Yes it is also possible to uplink the whole shooting match to glass aircraft - sort of removes the drivers airframe from the loop to a large extent: who selects how much you flex/ de-rate which V1 to use ,anti - ice, flap settings etc... Getting the correct information to the a/c is important then let the people in front make the plan.
Yes we have to do change figures when it`s unavoidable - runway change, sudden rainstorm with a now wet runway. Why leave the gate with something so important still incomplete? If you are still at the gate and you are not 100% happy there is no pressure - I`v been in a situation where we opened the cargo doors to double check due to a 2nd ACARS "final" loadsheet 15000 Kg lighter.
Less haste - More speed