I've been asked to send this patch to the list for review which I originally posted at rhbz#913446 [0].
My main motivation is to be able to set a saner default for dhcp leases in Boxes for development machines where the instant volatility of the dhcp lease makes it impossible to reliably work with services after the machines have to be rebooted. One has to discover the ip again... setup ssh keys...
This patch is a first attempt so feel free to let me know if I'm aiming at the right direction.