Using commerce_currency_format() as a default in a currency format_callback

I'm working on a site with many free products, and we want to display the price as "Free" instead of $0.00.

I was hoping to get away with something like this, but this causes loops, and makes everything free, because commerce_currency_format() calls the callback.

/**
 * Implements hook_commerce_currency_info_alter().
 */
function mymodule_commerce_commerce_currency_info_alter(&$currencies, $langcode) {
  $currencies['CAD']['format_callback'] = 'mymodule_commerce_currency_format';
}

function mymodule_commerce_currency_format($amount, $currency, $object = NULL) {
  $rounded_amount = commerce_currency_amount_to_decimal($amount, $currency['code']);
  $rounded_amount = commerce_currency_round(abs($amount), $currency);
  if ($rounded_amount == 0) {
    return t('Free');
  }
  else {
    return commerce_currency_format($amount, $currency['code'], $object);
  }
}

I ended up with the following. mymodule_commerce_currency_format_standard() is a copy and paste of commerce_currency_format() with the callback deleted.

/**
 * Implements hook_commerce_currency_info_alter().
 */
function mymodule_commerce_commerce_currency_info_alter(&$currencies, $langcode) {
  $currencies['CAD']['format_callback'] = 'mymodule_commerce_currency_format';
}

function mymodule_commerce_currency_format($amount, $currency, $object = NULL) {
  $rounded_amount = commerce_currency_amount_to_decimal($amount, $currency['code']);
  $rounded_amount = commerce_currency_round(abs($amount), $currency);
  if ($rounded_amount == 0) {
    return t('Free');
  }
  else {
    return mymodule_commerce_currency_format_standard($amount, $currency['code'], $object, FALSE);
  }
}

function mymodule_commerce_currency_format_standard($amount, $currency_code, $object = NULL, $convert = TRUE) {
  // First load the currency array.
  $currency = commerce_currency_load($currency_code);

  // Then convert the price amount to the currency's major unit decimal value.
  if ($convert == TRUE) {
    $amount = commerce_currency_amount_to_decimal($amount, $currency_code);
  }

  // Format the price as a number.
  $price = number_format(commerce_currency_round(abs($amount), $currency), $currency['decimals'], $currency['decimal_separator'], $currency['thousands_separator']);

  // Establish the replacement values to format this price for its currency.
  $replacements = array(
    '@code_before' => $currency['code_placement'] == 'before' ? $currency['code'] : '',
    '@symbol_before' => $currency['symbol_placement'] == 'before' ? $currency['symbol'] : '',
    '@price' => $price,
    '@symbol_after' => $currency['symbol_placement'] == 'after' ? $currency['symbol'] : '',
    '@code_after' => $currency['code_placement'] == 'after' ? $currency['code'] : '',
    '@negative' => $amount < 0 ? '-' : '',
    '@symbol_spacer' => $currency['symbol_spacer'],
    '@code_spacer' => $currency['code_spacer'],
  );

  return trim(t('@code_before@code_spacer@negative@symbol_before@price@symbol_spacer@symbol_after@code_spacer@code_after', $replacements));
}

I'm not yet familiar enough with the internals to make any suggestions. I'm just hoping there's an easier way to do this, or maybe this is more of a support request.