The problem with that is the effort and time to clean the nails before welding on them.
Most nails are coated with a galvanized or blue oxide finish. All of that needs to go before welding because a good weld would not happen with those coatings in the way and welding on galvanized can produce a poison gas.
Maybe sand blasting the nails would help but it would be faster to weld fill small holes with the welder. I ran into that on the side trim holes on a 68 dart.
