Magento won't find the controller as it would search for `Mage/Customer/AccountController.php`. I guess the only way is in fact `require_once` a controller php class file. 

I think [**here you can find a complete solution for this**][1]. 

The other, much less elegant way is to copy the whole controller you want to extend, and let it extend `Mage_Core_Controller_Front_Action`.

Edit: Or `Mage_Adminhtml_Controller_Action` for admin area controller.


  [1]: http://inchoo.net/dev-talk/how-to-extend-magento-core-controller/