well doing a full job is complicated as the actual schema may be
skattered opver multiple xml files, but assuming that isn't thecase,
something like

<xsl:key name="g" match="xsd:group[@name]" use="@name"/>


then

<xsl:template match="xsd:group[@ref]">
  <xsl:apply-templates select="key('g',@ref)/*"/>
</xsl:template>

together with an identity template to copy the rest of the stuff.

Of course xslt never handles tags, despite the subject line.

David

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