According to XEP-0060 it is possible to use a XSLT file to add a element to Pubsub messages like this one or that one .
Apparently, the “pubsub#body_xslt” option should contain an URL pointing to a XSLT file and the XMPP server should do the XSL processing and create a Pubsub message with a element.
I’m wondering if Openfire supports this option. I haven’t tried though, because I have no idea of what such an XSLT file would look like. Basically, this hidden Pubsub capability would allow to use Pubsub with current Jabber clients thanks to the “pubsub#include_body”.