We know it's impossible. I mean to get an upgrade over Asamoah or especially Licht - it would cost fortune and we won't spend that much anytime soon.
Besides that ss spot we can't upgrade our 3-5-2 significantly. What we should do is improve our squad to be able to play 4-3-3 too. We lost Pepe and Conte says we can't play 4-3-3 without him which means we need hardworking RWF who'd be an upgrade over Pepe offensively too. Sanchez is my favourite for this position, he can play on both wings in 4-3-3 and ss in 3-5-2. He always works hard and he's very good going past defenders which we need a lot. He's a good assist man also.
Then during the next season Conte may choose which one he prefers to play. I believe we'd use 4-3-3 much more if we had players that suit this formation. Right now we lack CF and RWF which is a lot. With Llorente coming and maybe Sanchez we could use both formations without limits.
As for other positions I think we're packed really well. We could get a decent well built CB maybe and that's it. For LWB position we have 3 players already it's enough. I don't see any point in looking for vice - Pirlo because we have no founds to buy such a player. Pogba can fill his position quite well and Marrone should be given more chances in midfield too.
4-3-3:
Buffon/Storari
Licht/Caceres/Padoin - Barzagli/Bonucci - Chiellini/Bonucci - Peluso/Chiellini/DC
Vidal/Isla/Pogba - Pirlo/Pogba/Marrone - Marchisio/Asamoah/Giacch
Sanchez/Pepe - Llorente/Quag - Vucinic/Giovinco
3-5-2:
Buffon/Storari
Barzagli/Caceres - Bonucci/Marrone - Chiellini/Caceres
Licht/Isla/Padoin - Vidal/Pogba - Pirlo/Pogba/Marrone - Marchisio/Asamoah/Giacch - Asamoah/Peluso/DC
Llorente/Quag - Vucinic/Sanchez/Gio