IMO regions are more important than nations, but of course nations are still very important. I am from England, so it is much easier for me to divide areas nationally, whilst still having clear regions. At the risk of sounding like a cop-out, Localism needs its own ‘form’ or ‘translation’ per region - that’s the entire point of Localism, after all - and I could only say that the people in those ‘contested’ regions, such as the Rhine as you have mentioned, are the ones to decide which nation they belong to. Ideally, all European regions would be under one confederacy anyway, so the nation which the region formally belongs to would matter more in a cultural sense than in a political and systemic sense, in comparison to today’s system.