You can copy from record numbers to the label field on 2500 records, no problem, using the change/move/copy tool
Actually, these days I rely on the Accession numbers (in the temporary citations in preferences) that come from pubmed for the articles. It seems to find other reference types even if that field is empty, or you can sort on accession number and copy from record number to that field. You can select and show any record where the field is empty (sort library on the accession field). If my colleagues also do this, we have no problem co-authoring papers!