Hey - I'm a member of the multitenancy working group (wg-multitenancy). We're working on a project called the Hierarchical Namespace Controller (aka HNC - read about it at http://bit.ly/38YYhE0). This tries to add some hierarchical behaviour to K8s without actually modifying k/k, which means we're still forced to have unique names for all namespaces in a cluster - e.g., you still need dev-service and prod-service. But it does add a consistent way to talk about hierarchy, some nice integrations and builtin behaviours.
Do you want to mention anything more about what you're hoping to get out of hierarchy? Is it just a management tool, is it for access control, metering/observability, etc...?
Thanks, A