docbook-xsl looks like it might help out in this instance as it plugs into xsltproc through /etc/xml/catalog which should result in offline generation; testing to see if this results in a full offline build.
docbook-xsl looks like it might help out in this instance as it plugs into xsltproc through /etc/xml/catalog which should result in offline generation; testing to see if this results in a full offline build.