Although not from specific denominations, here are some different views on the necessity of Jesus' death:
1) The prophecy:
Jesus often foresaw and talked about his impending betrayal and death. For example, at Caesurea Phillipi, the watershed moment of Mark's Gosepl, it is said:
He then began to teach them that the Son of Man must suffer many things and be rejected by the elders, the chief priests and the teachers of the law, and that he must be killed and after three days rise again. -Mark 8:31
Some could argue that this was divinely given, and no matter what happened, this had to be fulfilled. This is often the basis of Judas Iscariot's innocence, as there had to be a fulfiller of this definitive deed, it was just unfortunate that Judas was the one who had to do it.
The reasons why this prophecy existed is all down to atonement. Jesus' mission is to take upon himself all of man's sins. He undergoes flogging, mockery, corruption, betrayal, isolation and death. Maybe it is not so much the death that is important, but the overall passion narrative, where he endures out of love for us. You could also argue that without the crucification, the resurrection would not happen (or at least not in the same light if it were to happen at old age). The importance of triumphing over the sins of man would not be possible without the resurrection, and therefore crucifixion.
The Sanhedrin were the puppets of the Roman empire, as well as people of religion and therefore the law. In the gospels, they are the questioners and accusers of Jesus.
Their main role was to prevent civil unrest. Jesus, who could easily be seen as an extremist, with his radical views as well as his associations with groups such as Zealots, would therefore provoced them, as he did with the turning over of the tables at the temple. In Mark 14: 1-2, the Sanhedrin plot against him.
He then began to teach them that the Son of Man must suffer many things and be rejected by the elders, the chief priests and the teachers of the law, and that he must be killed and after three days rise again.
This is at the time of Passover, which celebrates the freedom of the Jews from the oppressive Egyptian state. Likewise, Jesus poses the same threat against the Romans. His death is therefore required to suppress revolt before Passover by turning against him and removing him, by killing him.