Magento ifconfig block and dynamic assets

Data.php

<?php

/**
 * @category    Package
 * @package     Namespace_Package
 * @license     http://opensource.org/licenses/MIT
 * @author      Leonard Mocanu <leonard.mocanu@ymail.com>
 */
class Namespace_Package_Helper_Data extends Mage_Core_Helper_Abstract {

    /**
     * Get link tag
     *
     * @return string
     */
    public function getCssUrl() {

        return sprintf('<link rel="stylesheet" href="%s">', $this->_getConfig()->getCssUrl());

    }

    /**
     * Get script tag
     *
     * @return string
     */
    public function getJsUrl() {

        return sprintf('<script type="text/javascript" src="%s"></script>', $this->_getConfig()->getJsUrl());

    }

    /**
     * Get the config model
     *
     * @return Namespace_Package_Model_Config
     */
    protected function _getConfig() {

        return Mage::getModel('namespace_package/config');

    }

}

namespace_package.xml

<?xml version="1.0"?>
<!--
@category    Package
@package     Namespace_Package
@license     http://opensource.org/licenses/MIT
@author      Leonard Mocanu <leonard.mocanu@ymail.com>
-->
<layout version="0.1.0">

    <!-- HEAD -->
    <catalog_product_view>
        <reference name="head">
            <block type="core/text" name="namespace.package.css">
                <action method="setText" ifconfig="namespace_package/enabled_some_block">
                    <url helper="namespace_package/getCssUrl"></url>
                </action>
            </block>

            <block type="core/text" name="namespace.package.js">
                <action method="setText" ifconfig="namespace_package/enabled_some_block">
                    <url helper="namespace_package/getJsUrl"></url>
                </action>
            </block>
        </reference>
    </catalog_product_view>
    <!-- //HEAD// -->

    <!-- SOME BLOCK -->
    <catalog_product_view>
        <reference name="product.info.addtocart">
            <block type="page/html_wrapper" name="product.info.addtocart.some_block.wrapper" translate="label">
                <label>Some Block Wrapper</label>
                <block type="namespace_package/product_view_some_block" name="product.info.addtocart.some_block" as="some_block">
                    <action method="setTemplate" ifconfig="namespace_package/enabled_some_block">
                        <template>namespace_package/some_block.phtml</template>
                    </action>
                </block>
            </block>
        </reference>
    </catalog_product_view>
    <!-- //SOME BLOCK// -->
</layout>

Couldn't add CSS and JS with addItem 'cause they're external.