Yeah, this is something strange to me. LvG plays 3412 due to the personnel in the team and getting the best out of his best players.
Let's assume, best players = Rooney, van Persie, Mata.
If you don't pick one or two of your best players (no longer needing to find a system to fit them all in) why do you pick the more unconventional system (other than continuity for continuity's sake)? You could argue that we don't have world class wingers, but I don't think people would be too unhappy to see Valencia and Januzaj on the flanks, with Rafael/Jones and Rojo at full back...
If you're thinking of a line-up and want to drop Mata, you should probably look at going 4231/4411. If not, then the only logical changes are Kagawa in for him, or playing Rooney there with van Persie/Welbeck up front. Maybe Januzaj in the hole, or Herrera/Fellaini? None of this seems like a straightforward improvement for me after one Premier League game.