1. repairing bad IGES geometry (big dihedral instead of tangency, gaps between surfaces that can not be zipped) by creating pattern of datum curves and exporting these curves to IGES. After that we use scantools for best fitting of new style surfaces to imported IGES (low density in scantools) curves. What you get there is smaller number of surfaces, better manufacturability. What you loose is that you get an approximation of original surfaces. Results are very good.
2. When making dieface tool one wants to have as small number of surfaces as possible an more important extends (usually greater than 5 mm) on the edge of the sheetmetal part. If the geometry is imported, then it is almost impossible to quickly extend the surfaces. Clasical methods (extending existing boundary curves and creating surfaces by boundaries) results in poor geometry which isusually nontangent. What we do is create quite dense grid of datum curves on the part and not so dense grid of curves which are extended from part out for let us say 30-40 mm and are tangent to original part. Both grids are used in scantools for building a good approximation (less than 0.05 mm) to original part.
3. Reverse engineering.
If you have organic shapes then use a software that makes untrimmer surfaces out of point cloud (Geomagic, Paraform,...).
If you want to make shapes like ball, cone, extrude,... out of point cloud with best fitting of basic shapes on it, you should wait for Pro/E Wildfire restyling. It is nice.