select 
--xmlserialize(content
xmlelement(
  name "document"
, xmlattributes('ir' AS "type")
, xmlagg(xmlparse(document '<'||t.n||'>'||t.v||'</'||t.n||'>'))
)
--as varchar(4000))
from table(values '
<document type="ir">
  <XNODE n="F1_2_1" o="55">Complex</XNODE>
  <XNODE n="F1_3_12" o="10">123456.00</XNODE>
  <XNODE n="F1_3_12_VAL" o="11">RUB</XNODE>
  <XNODE n="F1_3_14" o="53">5-10 yrs</XNODE>
</document>
') d(d)
, xmltable ('$d/document/XNODE' passing xmlparse(document d.d) as "d"
columns 
  N VARCHAR(20) path '@n'
, V VARCHAR(20) path '.'
) t;

select 
xmlquery('
transform 
copy $new := $doc
modify 
for $xnode in $new/document/XNODE
let $cn := $xnode/@n
return (
  do delete $xnode/@o
, do delete $xnode/@n
, do rename $xnode as $cn
)
return $new
' passing xmlparse (document t.doc) as "doc" ) 
from table(values '
<document type="ir">
  <XNODE n="F1_2_1" o="55">Complex</XNODE>
  <XNODE n="F1_3_12" o="10">123456.00</XNODE>
  <XNODE n="F1_3_12_VAL" o="11">RUB</XNODE>
  <XNODE n="F1_3_14" o="53">5-10 yrs</XNODE>
</document>
') t(doc);