modifications users drop-down list in admin

We have a WordPress site that has many subscribers. In the wp-admin area when you try to delete a user the next page has a radio button where you can “Attribute all posts to” and there is a drop-down of all the users. Looking to either modify or change the sql statement so that this drop-down shows only the users with a role of “Editor” is shown. We want the changes to be made in our child theme functions.php page so that when a new revision of WordPress comes out the changes will not be overwritten.