For 1.0 user event vs 1.0 restlet I think whatever argument you would have sent to the restlet that uses the netsuite plugin, like the POST body, you can set in a field on the custom record when creating it. A beforeSubmit user event can read that field value, do whatever the restlet would do, and set whatever value the restlet would return into in another field. The SS2.0 script can just look up the return value field after saving the record.