Ok, so I figured this one out after a few more hours and after sticking my nose into Magentos model classes. Seems product options was designed with a singleton pattern. Theres no need to reload the product in line 37:
$product = Mage::getModel('catalog/product')->load($product->getId());
…that was just a desperate try to deal with this problem. What I should’ve done is resetting the multiple options set in the Magentos singleton Product_Option instance. Replacing line 37 with the line below resolves the problem:
Mage::getSingleton('catalog/product_option')->unsetOptions(); // forget me and Magento will RAPE YOU
Hope this can save someone else some frustration. ;)
Magnus
2010-10-24 09:54:59