Now that I look at it, I think the Alaskan Bull Worm guy isn't in the first panel, but that's clearly him in the 2nd panel in between Saturn and Horseman, meaning the big shadow creeping down in the first panel is Imu, whose eyes are above everyone in the 2nd. So Imu has a transformation as well, we just won't see it for a while, unless that's some kind of hybrid worm man form. Horse dude is in centaur mode it looks like, so maybe but I'm betting that's actually Imu. It is weird, probably just an oversight by Oda that wormy isn't in the first pic
I think at this point, it's too late for another addition to the main crew. Like, yeah Yamato was around for the raid in Wano, but missing so much time by not being there for Egghead, it just feels like it'd feel too late if he were to join up after Egghead, and especially so after Elbaf
Personally, I hope they don't fully fight the Gorosei right now, I think narratively it works better if they just stall them long enough for the message to get out and then leave. Cause Luffy can't even damage them, if they get to the level of Franky being able to beat one, that'd be kind of a let down for right now.