Based on the reply : Create a new workgroup for the manager. Create a workgroup and associate the Manager to the workgroup. For the other workgroups make add this manager to the manager role.
In terms of workbaskets which are belonging to both the workgroups , add these workbaskets manually to the Managers operator profile. In this way all the operators and the manager can work on the same cases using get next work.
The only drawback is when u need to display the workbaskets for the manager. In that case define a new portal for this manager and display all the workbaskets in his profile.