Takeoff performance is predicated on your weight at the start of the takeoff roll.
It's reasonable to plan on burning X amount in taxi, when preparing your takeoff performance, based on the weight you will have when you reach the runway for takeoff. It's not reasonable to plan your takeoff performance based on the weight you think you might have at some point in or after the takeoff roll.
The ability to stop during a rejected takeoff isn't predicated on the weight after the takeoff roll, but the weight at the time of the reject. This means you plan for the weight at the start of the roll...not the middle or the end.