Riho Sayashi to join Babymetal?

DRK says:

This whole write-up looks at the situation from a Riho Sayashi POV. This is not the right way of looking at what has happened, given this is an international Amuse act and Riho, for all her popularity in Japan, is an unknown quantity, both to Amuse and Babymetal’s enormous international fanbase.

“Did Riho Sayashi join Babymetal? Maybe. No one knows at this point.”
No. She’s just one of three anonymous Avengers, there to give Su and Moa a helping hand and make things work, as a trio, on stage.

“Current Sakura Gakuin leader, Kano Fujihira, is another member of this Babymetal bullpen, with the third being unknown to me at this time.”
The third avenger is Momoko Okazaki, ex-Sakura Gakuin. BTW, Kano isn’t Sakura Gakuin’s leader; she isn’t Sakura Gakuin’s ace, ether. Both those positions are redundant when it comes to Sakura Gakuin. She is not necessarily the eldest member of the group. She is simply the President of the Student Council. The Student Council sees that things are running smoothly within the group and the President of the Student Council is the head honcho of the group and has a lot of powers and responsibilities within the group, unlike other idol groups.

“Amuse may wish to keep the spot for one of their own home-grown idols, though, which would be a bummer, because joining Babymetal would instantly make Riho the most successful ex-Musume ever.”
Amuse would, in all probability wish that one of their home-grown idols take that third spot. It is extremely telling that two of the three Avengers hail from Sakura Gakuin. They may also wish to give that third spot it back to Yui, in case she changes her mind. Though, there is every indication that they will give Koba a free hand and let him decide what to do as Babymetal has been his baby from the start.

“Even if offered the job, though, Riho would have to want to join Babymetal full-time, and that’s another thing we can only speculate on.”
What Amuse and Koba wants comes way before what Riho wants. Amuse will want what Koba wants, and, after the Yui episode, Koba will simply want to keep Su and Moa happy (given that they are the ones who will have to work with the third person concerned and the last thing he wants is either or both of them walking out, like Yui did) and they might not be willing to share with outsiders what they, together with Yui, have worked so hard to build up since they were teens. My guess is that this is the very reason for the existence for the Avengers.

“Further speculation would suggest that group management is looking for a full-time replacement for Yui, has narrowed the field of candidates to these three girls, and that these performances are a way to hold working auditions. I hope that’s the plan, anyway. I mean, they have to pick a third permanent member, don’t they?”
To answer your question: No, they do not. Perhaps Koba’s catering to the needs of Su and Moa, who, may not feel the need to share Babymetal with any outsider – that includes all the avengers. Let’s be honest, here: The avengers have not been formally introduced by Amuse or Brand Babymetal. They’re not given mics and not allowed to be present for interviews. Heck, they’re not even allowed to be photographed with the two permanent members. Notice anything strange with this picture: https://pbs.twimg.com/media/ECLJm3lU8AEprod?format=jpg&name=large or this interview: https://www.youtube.com/watch?v=qE0goaxIzOg ?

“Babymetal is an idol group; metal music is just the thing that sets them apart”
According to most normal human beings, perhaps. To Amuse and Koba, no. Koba’s done everything he possibly could to keep them apart from idols and j-music. He’s kept them away from TV. They’re not allowed to do collaborations with any idol act, including Sakura Gakuin! Rumours abound about an offer being made for a Kouhaku appearance in 2016 by NHK which was refused by Koba.

“Babymetal could hardly do better than Riho Sayashi to round out their team. Her dance skills are strong (as you can see in the video above), she has experience performing in front of large audiences as a center, she has name recognition from her time in Morning Musume, and she looks the part. Honestly, she’s perfect for the job.”
I feel that Kano Fujihira and Momoko Okazaki’s performance skills are as strong as Riho’s, when it comes to dancing, being highly familiar with Mikiko’s particular style of choreography.
Whilst they may not have the experience of performing in front of large audiences, the same has never deterred the original Babymetal trio and it will not deter the two SG avengers who share the same DNA as Su, Moa and Yui. Don’t forget that Su and Moa were Presidents during their final year in SG, as is Kano Fujihira, this year.
As for name recognition? Try telling that to Koba, who has done everything he possibly could to keep Babymetal apart from idols and j-music. Do you think for a second that this guy wants Japanese Hello!Project wotas?
As far as looking the part goes, let’s be honest: no she does not, not when placed side by side with Moa and Su who look trim, fit and toned like international superstars. To be honest, neither do Kano and Momoko.