From what I understand this is what you want to achieve:

1. You have a cluster admin access
2. You want to use this cluster admin access to create namespace admin(s)
3. You want these namespace admins to be able to grant access to other subject (e.g. users, groups or service accounts) to resources in that namespace.

If yes, then here is something you can try.

By default, your Kubernetes cluster comes with a set of default ClusterRole objects. In particular there are two default cluster roles that you will focus on:

1. edit
2. admin

Binding edit cluster role to a subject either by using RoleBinding or ClusterRoleBinding gives the subject access to edit most common resources like pods, deployments, secrets etc.

The admin cluster role however contains the accesses contained by the edit cluster role as well as accesses to additional namespaced resources, in particular to two resources that would be useful to administer a namespace:

1. Role
2. RoleBinding

If you bind this admin cluster role using RoleBinding to a subject within a specific namespace, you effectively give that subject the capabilities to administer the namespace, including creating another RoleBinding within that namespace to give some other subjects accesses to that namespace.

To illustrate:

You --(RoleBinding to admin ClusterRole)--> NamespaceAdmin
NamespaceAdmin --(RoleBinding to some Role or ClusterRole)--> OtherSubjects

Since RoleBinding is restricted to a specific namespace, the namespace admin will only have the admin accesses within that namespace only and cannot wreck havoc in other namespaces or at cluster level.