Got a somewhat acceptable wing by creating 4 profile sketches, then lofting them. Freecad can't create a solid from a surface, so you have to create 2D slices for the lofting operation, with matching curve & line segments. Freecad did manage to interpolate the sketches into a smooth curve. Suspect this process would be much easier to tweek & give smoother results if it was built up from equations rather than paw sketching, but the reference design is going to change. The automated version would have to use a constant number of line segments for each profile sketch instead of curves.