While Sakana does tend to hire talents with idol skills, he's also happy to hire sad girls who don't have idol talents. Muu is a prime example of this in Gen 3, for example. Sayu isn't going to be ruled out of joining Phase solely for lack of musical talent.
From the clips I've seen of Sayu, she does appreciate people who support her, and I think she would appreciate the support of a good group and some light wrangling. She's also streamed with a few different Phase talents already, and she has shown a positive response towards Phase Connect as a company, and it's not like she's ever shied away from expressing her opinions on anything or anyone. I think she's a likely Invader candidate.
