Delegation approval hierarchy
Whenever a line manager goes on extended leave or get suspended then his/her line manager role should be delegated to the HR Representative of his/her direct reports. The HR Representative should then be able to perform promotions on behalf of the line manager. But the approvals should still follow the line manager's hierarchy. For example,
Jimmy is the employee.
John is Jimmy's line manager.
Pete is John's line manager.
Mark is the HR Representative of Jimmy.
John goes on 3 months leave and delegates his role to Mark who is the HR Representative.
Mark then promotes Jimmy.