Specify an arbitrary multicast port for a cluster

Clustering is often used in tightly-controlled environments, where the Confluence administrator doesn't have complete control over the network environment. At the moment, the multicast address is generated by the cluster name via a hashing function; there's no feasible way to do it the other way around.
It would be particularly helpful if the multicast address could be specified as a system property on the command-line at startup or, better yet, in confluence.cfg.xml.