Is it possible to make Case Resources a smart group?
It uses whatever group is defined in
    &lt;custom_templates&gt;/CRM/Case/xml/configuration/Settings.xml

Just note that it needs to match the "name" field in the database in civicrm_group, which is usually different from the label that appears on screen. So if you create a group in the admin pages called "Ant Exterminators", the name might actually be "Ant_Exterminators_37". This would be true even if you deleted the current Case Resources group and recreated it - it might be "Case_Resources_43".

I tried it and it works with a smart group (at least on a slightly older CiviCRM version).