Need to allow Line Managers in Case Management 'Assigned To' field with restricted access

Summary:

We have a requirement in Case Management where Line Managers should be able to act as the overall case owner for their direct reports. Currently, the 'Assigned To' field is designed for Case Managers. If we provide this access to Line Managers, they would gain visibility into all cases across the organization, which is not acceptable.

The business need is to ensure that Line Managers can be selected in the 'Assigned To' field only for cases related to their team members, without granting them access to other employees’ cases.

Has anyone configured this scenario or implemented a workaround? Any guidance or best practices would be appreciated.