uwam2ie,
I may be misunderstanding your questions, but just to make sure we're on the same page, what you do is to copy the .pax file to any directory of your choice, I have edited several versions for different customers. Then you go into Perferences>Palletes and you add or remove palletes of your choosing from there, by browsing to the directory where you saved different .pax files. NX remembers your palletes for next time based on whatever you last had opened.
Whether you can swap between customers using roles or not is a different prospect that I'm yet to dabble in.
What you could do is to launch NX using a batch file so that if you have a file called "metric_drawing_templates.pax" that contains your drawing formats for customer A, and then you create another file of the same name in a different directory for customer B, then you could replace the file on disk with a saved copy from elsewhere depending on which customer environment you want to work with.
There are probably other ways to achieve this. As I said I'm not sure I'm on the right track, but let us know if it helps.
Best Regards
Hudson