Actually on the ground you are potentially in a life- threatening situation if you load the ZFW into the GW box of the FMC and use V speeds 10's of knots too low.This is the situation that the MEL Emirates crew found themselves in and although they survived the ensuing tailstrike,the aircraft was badly damaged and the crew lost their jobs.One of the contributory factors was considered distraction.
Noticeably the Emirates engineering staff will not interrupt the pre- flight procedure,briefings etc but wait until you turn to them.This is a direct consequence of the MEL incident referred to.I stand to be corrected but I believe that the Emirates cockpit is 'sterile' from pre-flight onwards.
atb