I've already seen plenty of comments on different websites with people stating they will buy SC6 because of this inclusion. The game plays great, can't imagine that people won't try out the other characters, even if they buy it just for 2B. From that point, it's only a matter of time they get hooked on the series, because IT IS very appealing to anime fans, especially women with the inclusion of Groh, who is basically Todoroki from MHA (most popular anime atm worldwide) and Raiden from MGS mixed together. Both are very popular with female fans and 2B is as well. Some of my friends already declared that they will buy the game after 2B announcement, because they are very attached to the character. It's a very good move, even if she doesn't really fit as well as Geralt, still they get more people interested in the game.
Also the DLC seems super cheap for what we're getting. I mean Tira costs less than a burger king meal in my country, and if you divide season pass price by 5 (3 chars, 2 sets of parts) it turns out to be pretty much the same.