Interesting, good question and comments.
I have attempted molding stainless steel fiber filled plastics for EMC, to replace expensive, ugly, and inconsistent spray coating, for very demanding, safety certification.
The surface conductivity was very inconsistent, depending on random SS fiber distribution. Also, molding process parameters of heating the tool results in a “skin” effect of neat resin with the SS fibers slightly below. Again end result is inconsistent surface continuity. SS fiber filled plastic injection molded housings of an electronic device failed near and far field EMC testing; copper painted interior, carbon spray coated exterior housings passed all tests, except visual aesthetic.
The injection molders disliked the material intensely. The SS fibers are magnetic and stuck to the screw barrel, machine cleaning was a huge effort. They are also very abrasive causing visible damage to machine parts in one sample run.
If I were to try again, I would try these nickel coated carbon fiber filled plastics.