Using Names and Matches together in XSL templates, we can choose and apply templates dynamically, based on content provided within the XML being transformed. I've searched for ages on how to do this properly, and a number of sources led me to this solution.

data_1.xml

<data>
    <datasource>
        <section handle="test-section">Test Section</section>
        <entry>
            <page-path handle="about">/about</page-path>
            <page-title handle="about">About</page-title>
            <title handle="about-this-company">About This Company</title>
            <template>
                <item id="2" handle="content" section-handle="page-templates" section-name="Page Templates">Content</item>
            </template>
        </entry>
    </datasource>
</data>

data_2.xml

<data>
    <datasource>
        <section handle="test-section">Test Section</section>
        <entry>
            <page-path handle="about-history">/about/history</page-path>
            <page-title handle="history">History</page-title>
            <title handle="the-history-of-this-company">The History of This Company</title>
            <template>
                <item id="4" handle="article" section-handle="page-templates" section-name="Page Templates">Article</item>
            </template>
        </entry>
    </datasource>
</data>

data_3.xml

<data>
    <datasource>
        <section handle="test-section">Test Section</section>
        <entry>
            <page-path handle="contact">/contact</page-path>
            <page-title handle="contact">Contact</page-title>
            <title handle="contact-this-company">Contact This Company</title>
            <template>
                <item id="3" handle="contact" section-handle="page-templates" section-name="Page Templates">Contact</item>
            </template>
        </entry>
    </datasource>
</data>

transform.xsl

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<!--
    Create a variable of this document's templates
-->
<xsl:variable name="content-templates" select="document('')/*/xsl:template"/>

<!--
    Match on a content node from the XML
-->
<xsl:template match="*[section/@handle = 'test-section']/entry">
    <xsl:apply-templates select="$content-templates[@name = current()/template/item/@handle]">
        <xsl:with-param name="node" select="."/>
    </xsl:apply-templates>
</xsl:template>

<!--
    A Template to output content as a 'Content' style page
-->
<xsl:template match="xsl:template[@name='content']" name="content">
    <xsl:param name="node"/>
    <h1>content template called!</h1>
    <h2><xsl:value-of select="$node/page-title/text()"/></h2>
</xsl:template>

<!--
    Template to output content as a 'Contact' style page
-->
<xsl:template match="xsl:template[@name='contact']" name="contact">
    <xsl:param name="node"/>
    <h1>contact template called!</h1>
    <h2><xsl:value-of select="$node/page-title/text()"/></h2>
</xsl:template>

</xsl:stylesheet>

That's really cool too! Nice approach.