With the current airfield technology available, why can't they design weighing pads at the parking stands that will give an aircraft's weight dynamically to within a given acceptable tolerance e.g (+/- 1000kgs) and displayed on a board somewhere that all can see.
Oh no, not again. This is one of those topics that comes up eventually after every tailstrike. Do a quick search and you'll find plenty of threads that answer this question. Quick answer: who is going to pay for it and why?