If you construct map entries for each use and then combine them into a

single map using the "use-first" or "use-any" "duplicates" option then you can
blindly process all the references and let the map-merge process produce a
single list of elements, e.g.;

<xsl:variable name="use-entries" as="map(*)*">
   <xsl:call-template name="find-all-conrefs"/>
</xsl:variable>

The find-all-conrefs template generates maps, one for each id/element pair,

which you can create with xsl:map or using the literal map constructor:
"map{$key : $value}".

Now make a single map:

<xsl:variable name="use-map" as="map(*)"
   select="map:merge($use-entries, map{ 'duplicates' : 'use-any'}"
/>

And then process the entries to produce the result docs:

<xsl:for-each select="map:keys($use-map)">
   <xsl:variable name="key" select="." as="xs:string"/>
   <xsl:call-template name="make-result-doc">
     <xsl:with-param name="key" as="xs:string" select="$key"/>
     <xsl:with-param name="key" as="element() " select="map:get($use-map,

Isn't that second parameter supposed to be named
       <xsl:with-param name="value" as="element() "
select="map:get($use-map, $key)" as="element() "/>
?

   </xsl:call-template>
</xsl:for-each>