I would like to create an operator and grant him/her the access to the OOTB reports for a selected set of deliveries.
Could anybody suggest the best way to achieve this ?
You can grant access to selected set of deliveries by creating a storage folder for those deliveries.
Then Open Folder Properties --> Security --> Authorizations and provide 'Delivery Operator' access right to that folder.
Also, provide delivery operator right to your operator. Doing this will give access to your operator to this Delivery Folder.