Parsing JSON is supported in XSLT 3.0 so using the commercial versions of Saxon 9.7 you could use
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:math="http://www.w3.org/2005/xpath-functions/math"
exclude-result-prefixes="xs math"
version="3.0">
<xsl:output indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:mode on-no-match="shallow-copy"/>
<xsl:template match="data">
<xsl:copy>
<xsl:apply-templates select="parse-json(.)?*"/>
</xsl:copy>
</xsl:template>
<xsl:template match=".[. instance of map(xs:string, item())]">
<id name="{.?name}">
<xsl:value-of select=".?id"/>
</id>
</xsl:template>
</xsl:stylesheet>
Using the open source version of Saxon 9.7 (i.e. Saxon 9.7 HE) the following takes up the suggestion made by wero to use json-to-xml and shows how to implement the requirement:
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:fn="http://www.w3.org/2005/xpath-functions"
xmlns:math="http://www.w3.org/2005/xpath-functions/math"
exclude-result-prefixes="xs math fn"
version="3.0">
<xsl:output indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:template match="@* | node()">
<xsl:copy>
<xsl:apply-templates select="@* | node()"/>
</xsl:copy>
</xsl:template>
<xsl:template match="data">
<xsl:copy>
<xsl:apply-templates select="json-to-xml(.)//fn:map"/>
</xsl:copy>
</xsl:template>
<xsl:template match="fn:map">
<id name="{fn:string[@key = 'name']}">
<xsl:value-of select="fn:number[@key = 'id']"/>
</id>
</xsl:template>
</xsl:stylesheet>
Saxon 9.7 HE is available on Maven and from http://saxon.sourceforge.net/