My short answer would be no.
Using the 1861 secession as a reference point, if I am "getting it", Westphalian Sovereignty implies more sovereignty than even the more avid secessionists had in mind. Even a Confederacy might be too restrictive.
Frankly, my short answer required some quick research since I am as unfamiliar with the terminology as everyone else appears to be. :)
I am going to read up on it some more and if it jells into anything worthwhile, I'll get back to you.