There is a task for this http://jira.jboss.com/jira/browse/JBMESSAGING-381 currently scheduled for 1.2.
This is an easy one to do so if you vote for it, it increases it's chances of being promoted to an earlier release. (No promises).
For now, if you are programmatically able to send your messages as non persistent then there will be equivalent. Of course this won't work unless you have access to the client source code.
That's fantastic! I feel a bit like an idiot for not marking the messages as non-persistant in the producer, though ;)
Thank you yet again for the quick responses.