@Paul Smullen My feedback has nothing to do with authentication, but...
If you're going to be pulling a large volume of data (and I suspect you will be, because it's a data warehouse project), then you might want to consider using SuiteQL calls made via RESTlets. You'll be able to get larger responses (up to 5,000 rows at a time), and potentially more efficient responses as well.
I wrote about that approach here:
https://timdietrich.me/blog/netsuite-suiteql-restlet/