Drupal 7: Path argument mapping to $form_state['values'] default

MY_MODULE.module

<?php

/**
 * Retrieves a single form by the $form_id and maps path arguments to values.
 *
 * This function mimics the behaviour of drupal_get_form() however it also
 * provides a mechanism to map path arguments to the default values provided
 * to the form via $form_state['values']. This solves a massive problem with
 * the Drupal core ability to correctly handle forms with that have methods of
 * type "GET" (<form method="get">) correctly.
 *
 * For example, if the requested path is /path/to/form/abc123 where `abc123` is
 * a value that should be mapped to $form_state['values'], the
 * $path_arg_value_map should be an associative array where the key represents
 * the element name within $form_state['values'] and the value should represent
 * the integer position value to retrieve `abc123` from the path using arg().
 * Therefore, this function call should look like:
 *
 *   MY_MODULE_get_form('my_module_form_id', array(
 *     'first_value' => 3,
 *   ));
 *
 * @param string $form_id
 *   The form id.
 * @param array $path_arg_value_map
 *   An associative array of path segment arguments to map to the form's
 *   $form_state['values'] array.
 *
 * @return array|mixed
 *   Returns the retrieved and built form.
 */
function MY_MODULE_get_form($form_id, array $path_arg_value_map = array()) {
  $form_state = array();

  if (!empty($path_arg_value_map)) {
    $values = array();
    foreach ($path_arg_value_map as $element_id => $position) {
      $value = arg($position);
      if (!empty($value)) {
        // TODO: Determine how to best sanitize this data; for now this suffices.
        $values[$element_id] = check_plain($value);
      }
    }

    if (!empty($values)) {
      $form_state['values'] = $values;
    }
  }

  $args = func_get_args();
  // Remove the $form_id from the argument list.
  array_shift($args);
  // Remove the $path_arg_value_map from the argument list.
  array_shift($args);
  $form_state['build_info']['args'] = $args;
  return drupal_build_form($form_id, $form_state);
}