Reality and Football Manager + Fifa are different things.
We haven't the squad to build a tactic based with the 3 at the back. The last team capable to play with this tactic was the 2010/11 squad with Sagna, Koscielny and Vermaelen on defense, Eboue on the right, Clichy on the left - we can joke about everything, but 3-4-2-1 it's only an excuse to not be catalogued as a manager with defensive attitude because this is a tactic based on five defenders - Song and Fabregas on midfield with Nasri and Arshavin behind Robin van Persie.
Now we haven't the right players to play like Chelsea and other many teams in Europe. Bellerìn and Gibbs/Monreal can't guarantee an immense work on the flanks, on midfield we're too slow with Xhaka and Coquelin, too fragile with Elneny and Cazorla, too offensive with Cazorla and Xhaka and too uneffective with Coquelin and Elneny. Ramsey could be an option as half-winger on the right into a 3-5-2, but with this tactic I don't know where Ozil could play: not striker and not winger for sure.