Conte's primary target should be weeding out the silly mistakes our starting players are uncharacteristically making (Buffon, Bonnucci, Chiellini and most recently Pogba). If this severe lack of focus continues we'll continue to struggle regardless of what formation we use. We'll basically keep gifting goals like we did against Galata where we gifted one goal while using 3-5-2 and another while using 4-3-3. Lack of focus is our greatest weakness this season and we've been very lucky to get the results we've been getting with our santa claus attitude.
Assuming the silly mistakes are weeded out, the 3-5-2 would be working very well. It has been effective in every match as our plan A for years now with Bayern being the only exception. But since more teams are now parking the bus against us then we need to make a habit of the 4-3-3 switch mid-game if the need arises. With the 4-3-3 as merely a plan B we wont need to buy depth players for it we just need a full 11 and the players dont have to be world class rather just above average since they'll have to accept coming in midway through tough games.
We do not yet have a complete world class squad for either formation. But we are closer towards completing the squad for the 3-5-2 (including a powerful bench) than the 4-3-3 and our players are very much used to the primary formation.
Since we don't have a large wallet we cant expect Marotta to complete the squad for both formations but he should definitely keep his eyes open for cheap deals that could complement either plans while giving a priority to our plan A.
The 3-5-2 would be complete if we managed to buy a starter quality LWB (making Asa a great bench option), a Pirlo replacement, and a bench quality RWB (unless Isla reinvents himself) and another world class striker to partner Tevez.
The 4-3-3 would be complete (it doesn't need a bench since its a midgame plan B) would need a LB and a RW.
So depending on the market next Jan and Summer, Marotta should keep his eyes open for the best available cheap Tevez-like deals for: 1) a LWB starting spot (with ability to adapt for LB), 2) a RWB bench quality player, 3) a world class quality striker, 4) an above average quality offensive winger and 5) a pirlo replacement. The market will decide what we can get of these since we are poor.
Achieve these targets and you'll have a world class starting eleven for the 3-5-2, a very strong bench for it and a very strong bench for switching to 4-3-3 midgame if the need arises. If we continue without a Plan B we'll be in trouble when teams park the bus effectively. If we make 4-3-3 our Plan A, then we need to buy a lot of world class players for the starting eleven and an awful lot for its bench (we cant afford it).