New Administrator Role - User Admin

We need an "User Administrator" role that can add / remove non-admin users to the organization, but cannot create other administrators. Right now, in order to CSV upload new users, you must the the all-power System Admin. "User Group Admin" can provision products but not new users, so there's a gap between "100% control" and "I just need to add / remove standard users" that the new role would fix. Better yet, just let us create custom, granulated, RBAC roles.