Interesting post that mate. I think Silva and Chilwell help them a lot in regards the defence.
You're right though, the biggest question mark is Lampard. He got a free pass last season, but with the money spent, the expectation of the club will be he competes to win the league. If he cant they will go and find a manager who is able to do this. Simeone could come, or Allegri etc.
Chelsea are a ruthless club. Lampard sort of fulfilled his role last season, he brought through a number of players. To the management of the club- job done. If he starts slowly, pressure will build quite quuckly.