Hi,
I tried to use the wmi to filter the group membership in my lab without success.
Not sure if the WMI for the group membership can't be used on the GPO .
Similar case for your reference:
https://social.technet.microsoft.com/Forums/en-US/e3c7a206-a219-4e03-b927-932f0d21c04c/control-user-policy-per-computer?forum=winserverGP
I would do more research about it ,if there are any progress, i would update here!
So for now ,as you said a easier way to filter the group membership it is though security filter.
Best Regards,