3. 4-3-3 (with wing backs)
The main problem of playing Mata in a wider role is that he does not put in the defensive shift that is expected of a natural wide man. As a result, the formation will always be slightly lopsided. The solution to this problem can be to dispel the notion of wingers altogether, and playing Mata in a central role just behind the striking duo of Rooney and van Persie.
Rafael and Evra can play as full backs with Jones, Carrick and Fletcher forming a defensive minded midfield trio needed to cover in case the fullbacks are caught out of position venturing forward. The alternative is to employ Evra and Rafael as wingbacks, giving them a lot more freedom to express their attacking abilities. Jones consequently will drop further back to form a three-man defense with Vidic and Evans.
While this seems like a left-field idea, it might actually provide a nice balanced outlet to best utilize the talents of the attacking triumvirate.