West Ham United are reportedly gearing up for a very big summer transfer window indeed. Julen Lopetegui needs to make big changes to the West Ham squad, after years of poor planning from David Moyes. We told you yesterday how Lopetegui has been given the remit of getting the Hammers back inside the top six in the Premier League. In order to achieve that, the Spaniard is allegedly prioritising moves to strengthen his back four and the centre-forward department. West Ham have achieved great success over the past four years, relatively speaking, and now Lopetegui faces the task of matching what M…