What is your use case?
Pods won't appear as hosts normally, only if you use PaaS Monitoring and don't install an agent on the worker node or use the operator.
There also is enough meta data for things like process group separation in k8s anyway, so host group separation shouldn't be needed for it.
Well, host groups can only be applied to the worker nodes not on a pod level.
But tags and management zones are pretty easy to setup. You can filter/tag based on all the criteria of the pods like namespace, pod/container name, k8s labels already on the pods, ....
So very few rules should be needed.