Pass bundle as URL argument

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My search brings me to line 449 in inline_entity_form.module:

  // Build the appropriate widget.
  // The "Single value" widget assumes it is operating on a required single
  // value reference field with 1 allowed bundle.
  if ($widget['type'] == 'inline_entity_form_single') {
    // Intentionally not using $settings['create_bundles'] here because this
    // widget doesn't care about permissions because of its use case.
    $bundle = reset($settings['bundles']);

If I change the reset($settings['bundles']) to the name of my custom entity bundle (e.g. 'other') - the IEF widget loads a form from the desired bundle. I have to extend this bit to accept arguments from URL (permission checks and security to be dealt with later).

UPD 1. The dirty hack works with the url /node/add/quote/other:

if (arg(3)) { $bundle = arg(3); }
else { $bundle = reset($settings['bundles']); }

Woohoo, now I shall test it for "coodies", make it configurable and would like to hear your opinions.

UPD 2. The bad thing is that if I use any Ajax buttons on the main node form (e.g. "Add more" for a field collection) - the arg(3) gets lost and field validation on Request submit works for the first bundle only.
I need to find a way to store the bundle argument on inline form creation.

UPD 3. So, the way I found around AJAX buttons screwing with arg(3) is to store the desired entity bundle within the $form_state.
Replaced the same line 449 from $bundle = reset($settings['bundles']);. Still crude, but effective.

if (arg(3)) { $ebndl = arg(3); }  
$array = $field['settings']['handler_settings']['target_bundles'];

if (in_array($ebndl, $array)) {
    $bundle = $ebndl;
    $form_state['inline_entity_form'][$ief_id]['form settings'] = array( 'bundle' => $bundle, );
} else {
    $bundle = $form_state['inline_entity_form'][$ief_id]['form settings']['bundle'];
}

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