What should be the best practice/process to be follow while an employee/approver is being terminated

Hello SMEs,

Can you please let me know the best practice/process to be followed (in requisition and PO approval ) where an employee/approver is being terminated.

To clarify further here are few scenarios

1) The approver is already end dated but there are pending approval notification against that approver (for requisition and POs)
      How to reassign those transactions.

      At present we have quite a few requisition workflows that are in error due to one of the following reasons -

      1 - Requisition preparer is end dated - Error - Activity 'REQAPPRV/547130' has no performer.

      2 - Requisition Approver is End dated - Error - 'xxxxxx' is not a valid role or user name.