Use Ajax with add more button to append textfields to Bean form

I'm trying to add more textfields to a bean form using an "Add More" button with an ajax callback to keep adding textfields to the fieldset.

Watching the ajax response in Chrome's Network tab, it doesn't contain the markup to replace the contents of fieldset-add-more-wrapper. I'm wondering if this is even possible with a bean form?

<?php

class ExampleBean extends BeanPlugin {
  /**
   * Declares default block settings.
   */
  public function values() {
    $values = array(
      'fieldset_add_more' => array(
        'text'    => array('value' => ''),
      ),
    );

    return array_merge(parent::values(), $values);
  }

  /**
   * Builds extra settings for the block edit form.
   */
  public function form($bean, $form, &$form_state) {
    $form = array();

    /*  Fieldset Add More Settings */
    $form['fieldset_add_more'] = array(
      '#type'               => 'fieldset',
      '#tree'               => 1,
      '#title'              => t('Fieldset Add More'),
      // Set up the wrapper so that AJAX will be able to replace the fieldset.
      '#prefix' => '<div id="fieldset-add-more-wrapper">',
      '#suffix' => '</div>',
    );

    // Build the fieldset with the proper number of textfields. 
    // We'll use $form_state['num_items'] to determine the number of textfields to build.
    if (empty($form_state['num_items'])) {
      $form_state['num_items'] = 1;
    }
    for ($i = 0; $i < $form_state['num_items']; $i++) {
      $form['fieldset_add_more']['text'][$i] = array(
        '#type'               => 'textfield',
        '#title'              => t('Textfield '.$i.' Title'),
        '#description'        => t('Adding textfield '.$i),
      );
    }

    $form['add_more_button'] = array(
      '#type' => 'submit',
      '#value' => t('Add one more'),
      '#submit' => array('example_ajax_add_more_add_one'),
      
      // See the examples in ajax_example.module for more details on the
      // properties of #ajax.
      '#ajax' => array(
        'callback' => 'example_ajax_add_more_callback',
        'wrapper' => 'fieldset-add-more-wrapper',
      ),
    );

    return $form;
  }

  public function example_ajax_add_more_add_one($form, &$form_state) {
    $form_state['num_items']++;
    $form_state['rebuild'] = TRUE;
  }

  public function example_ajax_add_more_callback($form, $form_state) {
    return $form['fieldset_add_more'];
  }

  /**
   * Displays the bean.
   */
  public function view($bean, $content, $view_mode = 'default', $langcode = NULL) {
    $content['block']['#markup'] = theme('example_bean', array('form' => drupal_get_form('example_form', array('config' => $config)), 'bean' => $bean));
    return $content;
  }
}
?>