There's a really east to implement procedure that would be a great aid to avoiding a gross error, and that would be for the optimum takeoff figures for the expected runway (which is already included in the flight plan) and the planned ZFW and fuel load to be included in the printed flight plan immediately above where the actual figures are to be hand written.
These figures would not be used by the operating crew other than to provide a crosscheck with the figures they come up with after recieving the latest information (actual ZFW and runway/weather conditions.)
It wouldn't be fool-proof. (For instance, the runway actually used is frequently different to the one planned, and notams may or may not become an issue.) However, it would provide a gross error check, and I can't help but think this would be more useful than both pilots doing separate calculations immediately before engine start.