NOTE: I don't mind this film. So lets say the film stayed the way it is. Basically, this is the "middle" film for the original trilogy. What they should have done was to add more robot scenes, and when Optimus died that was the perfect chance to allow the other Autobots shine and see their emotions and decisions about their fallen leader. What they SHOULD have done was cut all the stupid Sam's mum scenes, alice, and leo and his crew. I dont mind the twins because they have character. This film was a perfect opportunity to allow the other autobots shine.
They shouldn't have killed Optimus at all to be honest it was too soon and at that stage a third film was pretty much confirmed so their was little tension. The death of Optimus was also contradictory considering that they could have revived him and their are several scenes where the Fallen could have easily killed Optimus however chooses not to after he is resurrected.