Re: import entire tags

The page source looks now like this:
      ...
      <option xmlns:xspdoc="http://apache.org/cocoon/XSPDoc/v1" xmlns:esql
="http://apache.org/cocoon/SQL/v2" xmlns:xsp="http://apache.org/xsp"
xmlns:xsp-request="http://apache.org/xsp/request/2.0" value
="17">blabla</option>

Is there a simple way (I mean "short code") to avoid this kind of output?

xsl:copy-of unconditionally copies namespace nodes.
You try to can avoid this by using element constructors
instead of copying:
 <xsl:template match="*">
   <xsl:element name="name()" namespace="namespace-uri()">
    <xsl:copy-of select="@*">
    <xsl:apply-templates/>
   </xsl:element>
 </xsl:template>
Beware, untested, check against the spec before use.
You can omit the namespace bit if your elements are always
in the default namespace.

You can try to merge the stuff above somehow into your existing
transformation, or use it as a separate filter transformation
in the pipeline. Either way costs performance.
Another way would be to write a simple customized transformation
stripping superflous namespaces directly from the SAX events.
There are examples of similar transformers in the Cocoon
distribution (somewhere, well hidden). This should be the most
performant solution.