Allow a non manager fill in performance documents on behalf of the manager

Summary:

The need would be to have another role such as the Line Manager one so they could fill in the performance documents instead of the "real" line manager.

Content (required):

Hello,

We have a usecase that cannot be satisfied by the solution and we would like to hear from others on how they managed it.

Currently, some managers have many direct reports (more than 50 sometimes), so many performance documents to fill in as well. Some people in the organization, who are not managers (and don't have the line manager role), are identified to help line managers completing some administrative tasks. As they do not have the line manager role, they cannot access to the documents and fill them in.