Well I would agree with you if you meant Francia Media (the large kingdom stretching from the Low Countries to Italy), but Lotharingia (was named after the second eldest son of emperor Lothar king Lothar II.
The area of Lotharingia (Low Countries, Lorraine, Alsace and parts of the German Rhineland) did in fact have an identity, this region was part of the Frankish heartland. So IMHO Lotharingia could have had a chance, even with the powerful kingdoms of the Eastern Franks and Western Franks as neighbors; although a surviving Lotharingia could have ended up in similar way it's southern neighbor Burgundy did.
Middle Francia is really messed up, but Lotharingia the smaller central state...
It might cover the Frankish heartland, in the sense of the Franks as a people, but that's like covering the Slavic heartland (including the sense of being torn between being neither Western Frankish - what became French - or entirely Eastern Frankish - what became German. At least both were of the same branch of Christianity, but its still a division - though possibly less of one if one or the other halves becomes a dominant influence or some developments make for an identity of its own.).
I don't see that as a very viable start. Too easy for it to break up into pieces which may have their own identity but which aren't tied to the other pieces. http://www.sehepunkte.de/2010/07/druckfassung/17793.html (Now, I wish I could read outside English, because being able to find and quote from Schneider would be useful - in English there's this: http://theses.gla.ac.uk/2847/ which argues a lack of "Lotharingian"ness. )
Now, a set of strong kings, assuming Lotharingia isn't gobbled up by its neighbors first (which is a different sort of problem, in some ways) might be able to resist that. But a set of strong kings might see a king of Poland as Emperor of the HRE the same way James VI of Scotland became King of England as well - to pick an entirely possible as opposed to ASB scenario, but not a likely one.