A wiki-based journal is already operating: Ancilla Iuris (www.anci.ch, or www.doaj.org/doaj?func=findJournals&hybrid=&query=ancilla+iuris )

They use dokuwiki and a blog plug-in.
http://wiki.splitbrain.org/wiki:dokuwiki
http://wiki.splitbrain.org/plugin:blog .

(seen on the BOAI mailing list)