How to add another option to promote an article content to?
form_alter will allow you to add another option 

eg


hook_form_alter(&$form, &$form_state, $form_id){

     $form['my_field]['#options'][] = array('id' => 'value');

}


however, that in itself will not promote it, just allow you to set a value that can be picked up by a view or other means