City also needs to replace Haaland. If Haaland gets injured, City's performance will become erratic. Guardiola will definitely have to pay attention to this aspect. After these two changes, Guardiola will have to take necessary steps to further strengthen City's defense.
I don't understand what you mean by "replace Haaland". Do you mean get a backup for him, or should they replace him entirely? There is not a single striker in the world right now that can replace Haaland. As good as Alverez is, he couldn't do it. Only Mbappe would be able to do that, and if both are on the same team, Mbappe will likely play on the wing.
City's attacking problems are from the wings. The wingers were not effective. Foden, Doku and Savio were not threatening enough and could not lead the attack. Hopefully for City, they will be in a better form next season because there are not many good available winger in the market.