Hi Paul,
No problem, I reckon it's an interesting topic!
In terms of actually viewing a PDF e.g. when the response content type is application/pdf, then I thought creating a new response tab might be the nicest solution. Although I think this would probably be best done as a feature request i.e. change to the source code, and may not actually be doable as a plugin.. but this was just my take on what you wanted, there are many other ways to view the PDF with a bit of coding!
Good luck with whatever you choose to do and let me know if you need any help / suggestions, might experiment with the script route myself.... Probably others will want what you develop, will lookout for your plugin in the plugin library! :-)
Cheers,
Rup