Is there a tool that will allow PN to do an XSLT transform on and XML file... I wouldn't of thought it would take much doing if there isn't one out there.
I guess, ideally, you just need to be able to specify 2 files to a tool that would process the transformation and pass the response back to the output window.
Couple this with the 'auto-closing' tag feature I understand is currently being developed, and I think that you will have an excellent XML / XSLT development environment.