Ability to reverse Work Order tracking entries/completed quantities

In the event that we enter in error a completion quantity which is too high, or even against the wrong WO, thus creating mythical stock and potentially impacting costs. We can use the Scrap Finished Goods routine to remove thesurplus, but a simple reversal option could be abetter way? We can un-book in POP GRNs, we can un-issue components from a work order, so why not un-complete finished goods?