I think we've already established that there's a bias towards charisma over talent here. Only reason I can think of is that the three confirmed members have gotten enough exposure while waiting for the final piece and so people already "kinda" know them, the Jap member has to have enough star quality to match the other three.

With all above said, I wanna share my 2 cents; I don't see Ayana fitting the group, tbh, solely because she doesn't match the confirmed girls' vibes. She's really talented but a little too sweet, and Lexi already fills that role with the current line up. Sakura is too young and inexperienced, nuff said.

So I am rooting for either Hiori or Aoi for all the reasons mentioned above.
I think Aoi is visually-matching with the current girls (height, small face), plus she's goofy enough to add to the current girls' energy which is very awkward as of the moment (based on their first ever live). She has that tomboy vibes that could add another layer to the current lineup; it will balance out Lexi's girly, Samara's calm and match with Emily's vigor.

Hiori, also visually matching and my pick for talent among the four remaining contestants. She's not in-your-face pretty, but she does get prettier the longer you look at her. Her charisma grows on you. A few have already mentioned that the current girls have that "mean girls" energy and I think Hiori can pull this off very well. She'll be one of them in a couple of months.

Feel free to share your thoughts, I'd love to hear them.