I agree the stringers probably dont stop at the butt joints, but they stop somewhere. And it wouldn't be a Frankinblanik if factory pieces and drawings are used or approved splices are made. The problem wont be the stringers or skin. It will most likely be the lack of fit of the predrilled parts and shape differences. They were probably hand fit and drill back in the day, so not exactly the same between two individual aircraft. An early 737 is tough to swap sheetmetal parts. New aircraft, not so much because of cad design and computerized drilling.

I'll bet it can be done on the Blanik.
May not be a financial success however.
Many folks have had their fiberglass ship booms put back together. In my experience, sheet metal is much easier to repair or rebuild.