Magento won't find the controller as it would search for Mage/Customer/AccountController.phpMage/Customer/AccountController.php
. I guess the only way is in fact require_oncerequire_once
a controller php class file.
I think there's a complete solution: http://inchoo.net/dev-talk/how-to-extend-magento-core-controller/here you can find a complete solution for this.
The other, much less elegant way is to copy the whole controller you want to extend, and let it extend Mage_Core_Controller_Front_ActionMage_Core_Controller_Front_Action
.
Edit: Or Mage_Adminhtml_Controller_ActionMage_Adminhtml_Controller_Action
for admin area controller.