Support read-only view of fields on node add/edit forms

I have a situation where I need to be able to show some fields on the node edit form, but only enable editing of those fields for certain user roles. However, even user roles that cannot edit those fields need to be able to see them while editing. The field_permissions module does not currently support this functionality, but I think it would be a worthwhile enhancement. I realize that adding this functionality could be a bit tricky, but as a possible starting-point, here's some code that I put into a custom "job" module to designate a few fields as read-only:

<?php
/**
 * Implements hook_form_alter().
 */
function job_permission() {
  return array(
    'modify restricted project fields' => array(
      'title' => t('Modify restricted project fields'), 
      'description' => t('Modify the agency name, labor category and assignment number fields on project pages.'),
    ),
  );
}

/**
 * Implements hook_form_alter().
 */
function job_form_job_node_form_alter(&$form, &$form_state, $form_id) {
  if (!user_access('modify restricted project fields')) {
    $form['field_agency_term']['#disabled'] = TRUE;
    $form['field_ogs_labor_category']['#disabled'] = TRUE;
    $form['field_assignment_number']['#disabled'] = TRUE;
  }
}
?>