Hazard would definitely take over the Theo role. With him, we wouldn't need a playmaker. We'd have a front three of Podolski, RvP and Hazard who could create for themselves and the others quite effectively. Wilshere just behind them would be charged with getting the ball to them quickly and letting them create and score.
If you got in Kagawa, OTOH, you could put him central and Theo or Wilshere wide right. He'd be able to push higher up than you'd expect Wilshere in the above formation. This attack would have slightly less technical quality, but potentially more goals given that all 4 frontmen are scorers.