There are no date codes anywhere, so it may be possible to shorten Simon's good long-boss wheel with skillful die grinder work. or add magnesium to JM's good short-boss wheel with a TIG welder, as long as someone had both wheels present at the same time for reference. Shipping to/from The Netherlands is the main problem- either mod shouldn't cost over $150 in labor.
I wouldn't worry about running a welded Campy on the street, either. One of my fronts has a weld, and that was done in the last century. Since then, its been over 150 mph several times without killing anyone. Racing Campys used a different mag alloy than the several versions of street wheels.