We need another Tevez level striker more than we need a WB substitute. Either way we are on a tight budget and should keep our eyes open for expiring contracts and underperforming or unsettled players. We should not demand that the team wins the CL because it is simply unrealistic given the financial gap between us and the top teams. What we can realistically demand is the scudetto and a QF or Semifinal finish in the CL. In the event of being lucky we might snatch a final or a trophy along with it but that should not be our primary target nor our expectation from Conte.
A sudden change of formation away from the 3-5-2 towards the 4-3-3 would be very costly financially especially that we finally have a complete squad suited for the 3-5-2 barring some lacking of quality subs in the WB position.
Switch for a 4-3-3 and you'll suddenly need to buy a left back, a left back sub (unless you think Peluso is good enough), right and left wingers in attack and substitutes for them, an overcrowded midfield, too many good centerbacks for two spots, and Isla players that dont have a place in the formation altogether (isla).
It'd be financial suicide for a team which is already struggling to compete with the financial giants of Europe. If we can barely afford our current squad we definitely cant afford a complete and unnecessary overhaul especially that the dreamers amongst us demand way too much from a club with this wallet.