Black shadow is so unoriginal it makes my teeth hurt. He's a generic guy is a solid black skintight blackbody suit with giant horns (compensating much?) and cloved feet (cloved feet only look cool on fawns, on a human, it looks horrible).
Goroh screamed originality in every way shape and form, he had a wide base of potential moves, the second most prominent character in the franchise, and he appeared in the melee intro (a spot shared with likes of Ridley) if anyone was going to be in, it would have been him. You can hope for a Black Shadow or Deathborne as a boss (a possibility, and more likely Deathborne), but not a playable character.
Pico may have had an impact on the series (no one's denying that) but Goroh was THE second character, if he didn't get in, I can't see Pico being more significant to the point of surpassing him (or more significant at all for that matter.)