It can not be realized with plugin. It will need to hack the core source.
qa-include/pages/admin-default.php (around L1717)
Before:
'value' => qa_lang_html('options/permit_moderators'),
After:
'value' => qa_lang_html('options/permit_admins'),
AND
qa-include/app/admin.php (around L506) qa_admin_single_click()
Before:
if (isset($useraccount) && qa_get_logged_in_level() >= QA_USER_LEVEL_MODERATOR) {
After:
if (isset($useraccount) && qa_get_logged_in_level() >= QA_USER_LEVEL_ADMIN) {