We already have way more characters than the plot requires which doesn't really matter since the plot is shit regardless. besides I thought you loved trolling, imagine the reaction all the Hayabusa x Kasumi would give when Ryu's wife shows up, there would angry fanfics and broken dreams everywhere.
It became shit when Hayashi took the chair. If you are adding a NG character...it would make more sense to actually have a character who had a natural impact. Rachel definitely had a natural impact in the story of NG. Momiji (Even though she's generic and overrated for who knows why.) had a natural impact to the story. If you want another NG character..you want someone who at least did some damage. Regent of the mask (Hate NG3's story.) would of been a delicious choice. He did damage, even though the story sucked.
Yeah I like trolling, but when it comes to issues like these as to why she should be added...everything just stops until I find a reason as to why you want that character.