Wasn't the 2P from Soul Calibur just a palette swap of 2B. 2B having very pale skin with white hair and a black dress, so the inverse of that would be tan skin with black hair and a white dress. In that case they aren't an established character, they were just a color variation. The same could be said about Dark Pit who originally was just a palette swap of Pit.

Additionally, this is a Nier raid, meaning everything is based on Nier. Stating the character is an "already established character" from another game, in this case Soul Calibur, isn't accurate to this topic.