MemberProfileFieldExtension.php

<?php

class MemberProfileFieldExtension extends DataExtension {

    public static $db = array(
        'SortOrder' => 'Int'
    );

    function updateCMSFields(FieldList $fields) {
        $fields->push(new NumericField('SortOrder', 'SortOrder'));
        parent::updateCMSFields($fields);
    }

}

SortableMemberProfilePage.php

<?php

class SortableMemberProfilePage extends MemberProfilePage {

    public function getCMSFields() {
        $fields = parent::getCMSFields();
        $fields->dataFieldByName('Fields')->getConfig()->addComponent(new GridFieldSortableRows('SortOrder'));
        return $fields;
    }

}

class SortableMemberProfilePage_Controller extends MemberProfilePage_Controller {
    
    
}