I changed the first part of the listForm method to allow multiple users, as a comma separated values list. Works pretty well. I don't know if commas can be part of a username, if they can, I guess you'll just have to manually delete those pages, or change the "explode()" separator (the first argument):
function listForm( $usernames, $reason ) { global $wgUser, $wgOut, $wgLang; $users = explode(",", $usernames); $pages = array(); foreach ($users as $user) { $pages += $this->getNewPages( $users ); } if( count( $pages ) == 0 ) { $wgOut->addWikiMsg( 'nuke-nopages', $usernames); return $this->promptForm(); } $wgOut->addWikiMsg( 'nuke-list', $usernames ); ....