In order to allow a preparer create requisition on behalf of any other requester, user have to setup "Purchase requisition permissions" and add the requester to the preparer.

However, while the worker leaves or new worker joins, user have to go back and update preparer - requester relationship.

There should be option that allows to enable a preparer to create requisition for all active employees. So it would not require to maintain permission for preparer and requester.