Hi MC1024,
The CPUID masks the CPU features that are visible to the VM's OS. This could be dynamically changed if you change the EVC mode and power on VMs. A vMotion is one of these events as you have found. Also changes in HW version will release new CPU features to a guest OS (up to the EVC limit)
Now rather than changing the CPUID which will require you setting cpuid.1.edx and cpuid.1.eax values, I would doubly confirm that the licensing is tied to the features the CPU supports. It would be normal to have licensing tied to the UUID of a machine but to a specific set of instructions seems a little brutal.
If you need to proceed then take a look at this post: Manipulating Guest CPUID
Kind regards.