English fluency is a must have now because there's a limit to how many talents the JP manager (papa gorira) can manage at once. There is no point in adding a JP only vtuber to the roster because the numbers are inherently smaller. Chuubas who can speak Japanese and English are pretty common anyways. There are more overseas weebs that understand japanese or enjoy watching JP vtubers than there are actual Japanese people who are aware of Phase Connect.
Sakana is lucky that the two exclusively Japanese talents he hired are good at streaming, have cross-cultural appeal and are basically fine with having a mostly overseas audience. He is also lucky to already have bilingual staff that can do more than just prop up a less productive branch so it doesn't cost him a lot to keep them around.
As a JP watcher I don't feel that the narrative that they're being neglected is true at all. They are probably disproportionately supported compared to the rest of phase, considering that they get high quality merch, in-house art assets, the occasional outside collab opportunity and a dedicated manager which is a situation at least comparable to other JP corpos. They also have very high membership and donation revenue compared to your average JP corpo 2view.
From how they've described it, the concept of "Phase JP" isn't a thing anymore. Iori, Nasa and Michiru are in the same discord as everyone else, sit in the same meetings and talk to EN talent every day.
The only thing I think they need to grow is just more exposure via clips and collabs, but the collab part is all up to them.
The clip part is up to (you).