This has to be done through the include files for the individual styles (eg, biblio_style_vancouver.inc). Therefore, this has to be done by the Drupal Cloud administrators, as Content Managers don't have access to this code. I would suggest that at least one of the 8 predefined styles be set to an artificially high default (40 authors, perhaps). If you're a faculty member and you're the 15th author, you still need to see your name listed on the list of authors. So I generally list all authors in a citation.