.. such systems have been around for decades ... on freighter operations, they can be a very useful backup to all the other systems when it comes to catching out significant errors.
However, as with any weighing system, the underlying technical considerations are accuracy and repeatability .. which go hand in hand with cost.
Overall, there is no real advantage in going to all the hassle and cost of setting up a reweigh standard on board system.
So far as using average weights is concerned, provided that the sample numbers are adequate, the residual errors are quite small generally.