We know what happened last time Italy played a 3-4-3 against Germany.....
But you're right, in some way the 3-4-3 would be the wisest considering Italy's available pool of players AND if Conte wants to keep the BBC intact. Only problem is that it might be too offensive, so it should be played more as a 3-4-2-1 with two attackers dropping deeper so the midfield doesn't get overrun. Also the tactics obviously change; the 3-5-2 has worked flawlessly with the 2 strikers up front, aswell as the midfield three has been absolutely essential to Italy's game. This is why I would rather keep the shape and just change one player, instead of the whole system. I trust Conte though....