A what-if question for you all, one that requires a little suspension of your skepticism. Say for whatever reason, by (points to a random year) 1919 WWI has continued but without American involvement. German forces still control Belgium and a good chunk of northern France. American mediators are asked to mediate a peace settlement since after this time both France and Germany have to deal with significant civil unrest. And just because someone might ask, the Eastern front went as in RL. Now to the real question I have for you all.
What if the Americans suggested creating an independent nation in Alsace-Lorraine to ease the tensions between France and Germany over that region. Obviously this would not be a welcome suggestion to either France or Germany but civil unrest might force them to this compromise and since Germany controls a part of northern France, the French (with a weaker bargaining position) might rather see an independent A-L rather than one administered solely by German. If this would happen, who would be likely to lead such a nation? Is there a particular Royal Family that could lay claims to such a nation? I'm guess if so, France would try to see it was one with little connections to the Germany Royalty so the Germans couldn't lay claim to it that way in the future.
There was actually a briefly independent nation of Alsace-Lorraine but it was communist so I'm guessing its leaders are out.