Three positions in midfield, Schweinstegier, and Herrera would have to be starters when fit, then the other position would be the attacking midfielder and for me Rooney (if we get a top striker in), or Mata will take that position. So we'd have Carrick, Schneiderlin, Fellaini, Mata/Rooney as back up, which is over kill imo.
ADM, and Pereira can also play there if needed too.
I'd be surprised if we don't get a top striker in as I think LvG just doesn't think Rooney is up to full time, but Rooney will have to play so I think he will rotate with the striker, and Mata.