Is possible to choose the file_default_scheme to save avatars?

Question

I'm using amazonS3 module and if I choose Amazon Simple Storage Service as my default download option, user's avatars are uploaded to my bucket in Amazon. I wish I could choose the default_scheme for avatars but checking the user_save function code I found these:

 if (!empty($account->picture->fid) && (!isset($account->original->picture->fid) || $account->picture->fid != $account->original->picture->fid)) {
    $picture = $account->picture;
    // If the picture is a temporary file move it to its final location and
    // make it permanent.
    if (!$picture->status) {
      $info = image_get_info($picture->uri);
      $picture_directory =  file_default_scheme() . '://' . variable_get('user_picture_path', 'pictures');

So I think that it uses the default scheme selected. Is it possible to change it?

Thanks