I was a mechanical engineer for my entire career, and admittedly am not up with the latest in 3D printing technology, but I would be shocked if a printed flight would hold up to the cold temperature impact and stress of this application. Even a molded part I would be very concerned about the design of the mold to avoid sharp edges or knit lines which would start cracks and cause it to fail over time. With 3D printing, you have a knit line between every layer of plastic, and that will reduce the strength of the part. I only got a plastic flighted bit recently, but not is clear the tips of the flights flex to prevent them binding on the edge of the hole.
Not trying to throw cold water on something I have never tried, but have you considered trying to get replacement parts from one of the manufacturers, and adapting them to a Nils head? That might be simpler, and you would get a molded part from a low temp impact resistant plastic.
If you are trying to design the ultimate hot rod auger head, there was a thread where a guy cut off all but 2 or 3 flights in addition to making an aluminum shaft. He found it reduced the drag of the flights on the side of the hole, and as long as you have enough to lift the bottom chips, the chips below push the rest up out of the hole. If you keep it spinning as you lift the bit out, you can clear the hole without a series of flights all the way to the surface.
The Nils is an amazing cutting head, and if you could pair it with an ultralight shaft and flighting system, I would be jealous!