Now that we know it's actually being worked on I guess it's a good time to speculate. I'm assuming Entergram is working on, so my speculation is being made with that in mind. Aquarium and Okayu Nyumu had short routes for the side characters, but since FuwaMoco are a duo I'm not expecting any guests. The routes will be the main FuwaMoco route where you romance them both, a short Fuwawa route and a short Mococo route you can get in the middle of the game, and a super short gag Pero route.
>>358
This timeline might not be too far off actually. Okayu Nyumu 2 is coming out about a year after the first one, so it's possible FuwaMoco's game could have a 1 year turn around time. They finally said they were making progress in September, which is only a couple months after July.
>>3382
While I think this artist being involved is probably not true since they followed him before any movement was made it could still be possible. Just because they hadn't had any official meetings at the time it doesn't mean they weren't putting in some work here and their looking for staff. And as you said this artists has worked with Entergram, so it works well with my thoughts that Entergram is making this game too. The only other thing that might disprove this though is I think Aquarium and Okayu Nyumu had the same artist. So that artist might just be Entergram's default when working with Hololive.
Anyways, I'm glad progress is finally being made. And if Okayu Nyumu is anything to go by, if the FuwaMoco VN is a success then there are also chances for sequels.