The midfield wouldn't be vastly different to what we're playing now. I mean, Gundogan presses just as well, if not, better than Herrera, and has better defensive qualities, and Mata is pretty quick too. However, I think being quick isn't important. It certainly helps, but when you're a team that presses high and only need to run say 5 yards to close a player down, then it's not a big issue. I mean, Xavi, Busquets and Iniesta weren't exactly the quickest midfield ever, but they were part of arguably the best pressing team ever.
That said, I edited my team because I really have a feeling Van Gaal will want to play Rooney as a 10/second striker, as we know he likes to play his CAM close to the striker when in possession of the ball.