I would suggest we will be relying on Foden as the false 9, a role he performed very well when asked in the past.Oscar Bobb is a winger. He'll be competing with the likes of Savio, Doku and Grealish.
Alvarez is a backup to Erling. One injury and suddenly we're relying on wingers who have never hit double figures in their careers to smash in the goals for us. Or Kovacic to suddenly turn into Gundogan.
I get people being optimistic but it is not a good idea.
We won the league twice with no centre forward before we signed Haaland, so I doubt it would unduly hinder us reverting back to that formation, if/when Haaland gets injured.