Using on field other than just user field

As I can see, this only works for fields in user account.
Why is it not possible to use it on all fields?
Or at least for fields defined in a profile2 page?
This could be implemented as a configuration option.

The following function I've changed from:

function user_role_field_form_alter(&$form, $form_state, $form_id) {
  if (isset($form['instance']) && $form['instance']['entity_type']['#value'] == 'user' && $form_id == 'field_ui_field_edit_form' && isset($form['field'])) {
    module_load_include('inc', 'user_role_field', 'user_role_field.admin');
    return _user_role_field_field_settings_form_alter($form, $form_state, $form_id);
  }
}

To:

function user_role_field_form_alter(&$form, $form_state, $form_id) {
  if ($form_id == 'field_ui_field_edit_form' && isset($form['field'])) {
    module_load_include('inc', 'user_role_field', 'user_role_field.admin');
    return _user_role_field_field_settings_form_alter($form, $form_state, $form_id);
  }
}

Also, there is need of altering the user_role_field_field_access function.
This is not a working solution, just some ideas.

What Do you think?