If networking is already configured when a VM boots, how about a kernel parameter for a configuration server? If it is configured to grab an executable file, it would be very flexible. We use kickstart files to build our CentOS VM's and physical boxes and then pull configuration changes from a server at regular intervals. I'm working on extending our existing internal intranetto keep history and to allow a single change to propagate to all relevant servers. Also would allow fail2ban to share it's banned IP's. Since this is specific to our internal systems, it can't easily be exported, but most of it is pretty straight forward. It could almost be integrated into an existing CMS. Think WebMin but in a LISA (Large Installation System Administration) environment. A similar technique could be used for cloud machines.