I love the idea of fixing up the old coup, it looks adorable and old fashion. I would also build a new one on the concrete.
We recently moved to country with 2 old coups, we fixed up the smaller 1 (8X16) and haven't yet decided wether to rebuild or fix up the larger 1 (12X16) since it is in much worse shape. Both of them also have electricity.
As you can see, the buildings are not in real good condition. The back house is the larger 1.