This is the weirdest thread in a while.
Icelanta on P1 of this thread is correct.
The fuel does NOT have to be burned prior to t/o. If the flight plan and load sheet were legal on dispatch, in the outfit I work for, the taxi fuel usage need not be considered provided any exceedance is consider to be minor. 500kg in 396000kg is minor IMO.
In our SOP there is NO requirement to check any aircraft weight indication just prior to t/o, this would rely on fuel indications being dead accurate, which they aren't, and the ZFW being dead accurate, which it isn't. Using actual passenger weights are we? No! The legalities are covered by the load sheet, the performance is covered by the margin of error built in.
I would expect that any wide-body departure on any day is actually +/- 2000kg of what you think it is.
Anyone who deliberately increases their brake energy before a max TOW t/o in a wide body should be removed from the line for remedial ground school training.
The OP wrote:
Widebody jet, 30 degrees C, full takeoff thrust required, max taxi weight but due to a runway change, the planned taxi routing runway is shorter than expected.
500 kg need to be burned before takeoff is legal.
This last sentence is the incorrect assumption. Take the 500kg into the air with you as a bonus.