I'd bet Storable would be able to persist an xmlnode scalar to disk, and read it back in, in a way that looks just like persisting any other datatype.

Storable does a fine job with complex data structures, including objects.

...just can't do [it] with XML::LibXML without going through a complete deparse/reparse cycle...

I don't believe that's avoidable.

...it'd take a lot more code...

I still don't buy it. Witness:

    my $xml_fragment = XML::Struct->new( <<EOF ); # fictitious...
        <records>
          <record id="001">foo</record>
          <record id="002">bar</record>
        </records>
EOF
    my @nodeset = $xml_fragment->xQuery( "//records[@id = '001']" );
    die "ids should be unique!\n" if @nodeset > 1;
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Why is that so bad?

In general, any suggestion that the core language should be changed to accomodate a specific domain or technology should be held at arm's length.