We're trying out 3-5-2 for two reasons, imo;
1 Our wingers are shit/underperforming
2 We have too many strikers (LVG's usual formation uses one striker which would mean dropping/moving one of Rooney and RVP)
So replacing a number 10 or a striker with a player like Di Maria would be great for squad balance, imo. Just because the squad is imbalanced, it doesn't necessarily mean we have to buy more defenders and sell attackers. We could improve the balance with Di Maria if we sell the right player. It would help us play 4-3-3 on occasion, because Di Maria is great out wide, but he is also more than capable of slotting into a 3-5-2.