All fair points, but the Fernandinho of last season was far from a peak Fernandinho. His legs had gone and in some games he was a bit of a liability sadly. Kalvin Phillips will replace last seasons playing version of Fernandinho no problem and will give us much needed legs and energy in midfield. He is a very viable option to rotate with Rodri and play alongside him too and that's what we need. I doubt he's the type of player that would rock the boat either if he didnt play every gane. I also think Phillips has got improvement in him too and we'll see that over the next few years should he sign.
What we can't replace with Fernandinho is his leadership skills. That aura around the dressing room will be missed and its where other players will need to step up just like when Kompany left the void in the dressing room.