Magento 2 – Use helper in layout

Currently the template is defined like this:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="CompanyPdfDesignModelCompanyDesign">
        <arguments>
            <argument name="templateFiles" xsi:type="array">
                <item name="extras" xsi:type="string">Company_PdfDesign::pdf/table/extras.phtml</item>
            </argument>
        </arguments>
    </type>
</config>

However, I want to make this dynamic and load it from the settings, so I tried to use a helper like seen here:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="CompanyPdfDesignModelCompanyDesign">
        <arguments>
            <argument name="templateFiles" xsi:type="array">
                <item name="extras" xsi:type="helper" helper="CompanyPdfDesignHelperTableExtras::getTemplate"></item>
            </argument>
        </arguments>
    </type>
</config>

But if I flush cache from CLI then I get alot of XML errors.

How can I load the value from a helper instead of hardcoding it?