Hi Lars!
To generate a new IOPlatformUUID for your Mac OS guests, there are two things you need to do:
1) Ensure that your deployed VMs have unique NIC MAC addresses. Mac OS uses the MAC address of the primary NIC to generate the platform UUID. Shut down the VMs and generate new NIC MAC addresses if needed.
2) Erase the NVRAM variable named platform-uuid. You can do this by running sudo nvram -d platform-uuid inside the Mac OS guest and then rebooting, or, if there's nothing else important in NVRAM (usually for Mac OS guests there is not), you can power off the VM and rename the .nvram file in the VM's directory to something else to completely clear the NVRAM.
Mac OS will generate a new IOPlatformUUID, based upon the MAC address of the primary network interface, when it next boots.
(You can reorder the above steps to suit your needs: The important part is that Mac OS will generate the platform-uuid when it detects that there is not already a platform-uuid present in NVRAM, and it will use the MAC address it finds at that time. It will not subsequently update the UUID if the NIC MAC changes.)
The easiest way to avoid this problem in future is to ensure that new NIC MAC addresses are generated at clone/deploy time, and simply omit the .nvram file from the clone/deployment.
Hope this helps!
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Darius