The reason I created the make_fog_portable script is because we have about 70 sites serviced by VirtualBox servers.
The Oracle VirtualBox VM has a fixed MAC address.
Each of these sites is on its own IP subnet with its own scope properties.
That particular MAC address has an IP reservation, bootfile configuration and a DNS entry at every one of those sites/subnets. This allows any OVB VM to work at any site.
The same goes with the physical servers. If we change the subnet for that site, the script would automatically reconfigure the server at next reboot.
This has the added benefit of my being able to create a FOG server in my DEV environment, on my private scope and not have to worry about configuring the server with the IP of a foreign subnet; I just configure the name.