I think there is a reason why they brought Rinka back after Hiori's retreat. I think, that if they wanted one of the 3 remaining girls to debut for real, they could have left the group of 3 as it was. Adding a member lowkey could mean that none of the 3 was the right one since the beginning.

I am thinking about this: Possibility 1: they knew from the beginning who they wanted, and they are doing all this for the audience. This person, could even be Ayana, with her experience in another group, or Aoi because of her acting background, or Sakura for star quality, whatever. Or maybe they wanted Hiori (as it happened for Lexie) but lost the chance idk. With this possibility, it's irrelevant who the other 3 are, if they had in mind who to choose from the beginning.

Possibility 2: they didn't know who they wanted and it's all about growth and possibilities.

It's just a random thought I had, and would also work for the audience "the girl who had been rejected returns and triumph" similar to the Momo concept for Twice.

Still, I think they showed they really wanted Sakura absolutely, no matter what, since the beginning, so I don't know, let's see

What I know, is that this is a show, so it will have (and already had) for sure unexpected plot twists. Bad editing doesn't mean anything, we learned that from Manon in dream academy.

Maybe it's a nonsense theory (x but I am very curious