What was The Illusive Man's Goal for Shepard in ME2?

I am fairly new to  the series and recently completed all three games for the firs time.  Anyway there is something that has been bothering me since completing ME2.  What was The Illusive Man's goal for Shepard in ME2?  I mean why did he want to bring back Shepard with his morality intact?  Why didn't he let Miranda implant a control chip into Shepard?  Why did he want an unaltered Shepard?  I mean when I played ME1 I was a full Paragon, did he not know that Shepard would not follow his extreme orders?  In ME1 Shepard killed many of the experiments done by Cerberus.  At the end of the Suicide Mission when The Illusive Man tells Shepard not to destroy the Collector's Base.  I was expecting TIM to pull the kill switch he secretly had implanted into Shepard's brain when he said no.  Instead TIM invested billions of credits to bring back Shepard, only to have him say no when TIM would tell him to do something extreme.  That makes no sense.  If I was TIM I would have installed a kill switch and then when Shepard is on the Collector base activate the switch once he refuses.  Also I know that TIM recruited Joker and Chakwas because they were familiar faces.  But did he not think that they would both betray him in the end?