Yes, had there been another way, the cup would have passed.
John Murray is spot on I think:
But having purposed to redeem, was the only alternative the blood-shedding of His own Son as the way of securing that redemption? There appear to be good reasons for an affirmative answer.
A. Salvation requires not only the forgiveness of sin but also justification. And justification, adequate to the situation in which lost mankind is, demands a righteousness such as belongs to no other than the incarnate Son of God, a righteousness undefiled and undefilable, a righteousness with divine property and quality (cf. Rom. 1:17; 3:21; 22; 10:3; II Cor. 5:21; Phil. 3:9). It is the righteousness of the obedience of Christ (Rom. 5:19). But only the Son of God. incarnate, fulfilling to the full extent the commitments of the Father's will, could have provided such a righteousness. A concept of salvation bereft of the justification which this righteousness imparts is an abstraction of which Scripture knows nothing.
B. Sin is the contradiction of God and he must react against it with holy wrath. Wherever sin is, the wrath of God rests upon it (cf. Rom. 1:18). Otherwise God would be denying Himself, particularly His holiness, justice, and truth. But wrath must be removed if we are to enjoy the favor of God which salvation implies. And the only provision for the removal of wrath is propitiation. This is surely the import of Romans 3:25, 26, that God set forth Christ a propitiation to declare His righteousness, that He might he just and the justifier of the ungodly.
C. The cross of Christ is the supreme demonstration of the love of God (cf. Rom. 5:8; I John 4:9, 10). But would it be a supreme demonstration of love if the end secured by it could have been achieved without it? Would it be love to secure the end by such expenditure as the agony of Gethsemane and the abandonment of Calvary for God's own well-beloved and only-begotten Son if the result could have been attained by less costly means? In that event would it not have been love without wisdom? In this we cannot suppress the significance of our Lord's prayer in Gethsemane (Matt. 26:39). If it had been possible for the cup to pass from him, his prayer would surely have been answered. It is when the indispensable exigencies fulfilled by Jesus' suffering unto death are properly assessed that we can see the marvel of God's love in the ordeal of Calvary. So great was the Father's love to lost men that He decreed their redemption even though the cost was nought less than the accursed tree. When Calvary is viewed in this light. then the love manifested not only takes on meaning but fills us with adoring amazement. Truly this is love.
Those who think that in pursuance of God's saving purpose the cross was not intrinsically necessary are, in reality, not dealing with the hypothetical necessity of the atonement but with a hypothetical salvation. For, on their own admission, they are not saying that the actual salvation designed and bestowed could have been enjoyed without Christ but only salvation of lesser character and glory. But of such salvation the Scripture knows nothing and no good purpose can be served by an imaginary hypothesis