Well, the truth of the matter is that custom Tav is the only playable character who does not exist in the game unless we choose to create them. The origin characters as well as DU exist within the game no matter if we're playing as them or not, so they always get to be important to the game and its story. But Tav is not important to the story, and CANNOT be important to the story by definition, because we can have playthroughs where Tav doesn't even exist.
DU does not exit if not chosen, as far as we know.
Also, your character *can* be important without existing beforehand.
Yes, other people can take his place. Does not mean Tav can not be important if existent.
There are options no PC aside from Tav & DU can take.
There are race tags not chosen by them. And if I understand it correctly, their class tags also do not change, even if you change their class.
So the class-tags are also unique to Tav/DU.
But even aside from that, the Main Character is *per defenition* important to the story. Even if that character would not exist if not chosen as a Main Character.
