Export Content as of a Certain Date

Currently when you export a wiki page or do a custom export of multiple wiki pages it exports the current revision of the document. We happen to keep many policies in our wiki and it would be handy if we were to be audited because of a complaint to be able to produce a copy of our policies that were in place at the time of the complaint. The pages are already revisioned, so it should be relatively easy to create the export as if it were a certain date in the past.