Gen 3:22-24 No Life without Death?

I have often heard people interpret Genesis 3:22 like this: God in his mercy prevented man from eating from the tree of life otherwise he would have lived forever in a state of sin. But I am uncomfortable with this for a number of reasons:

• It seems a too sophisticated intrepretation; there is a lot of logic involved in the statement above and beyond what is in the text.
• It attributes a 'magical' property to the tree itself, that by physically eating it eternal life is conferred, ex opere operato.
• It views 'live forever' only as meaning an unending physical life, a continuation of whatever current physical state is being experienced (kind of like the wind changing when you pull a face ;-)

Instead, I would prefer understanding Gen 3:22-24 as simply about cutting off man from life (and perfected life) as a consequence of sin. The wages of sin is death ('you shall surely die'), and not life, therefore man has no right to the tree of LIFE, and must be cut off from it. So 3:22 is not a mercy, but a judgement. The only way to life is God's way, and man lost the opportunity for life when he sinned. So man was sent out of the garden and cut off from the tree of life. (One wonders if the labour of 3:23 required of man indicates he is 'stuck' in the sixth day, and unable to enter the rest of God, in the perfected seventh day..?)
More tentively, I wonder if Gen 3:24 signifies that there will be no access to the tree of life, without first passing through suffering and death (the flaming sword wielded by the cherubim). This would seem a wonderful picture of what will happen in Christ, that he first dies before obtaining eternal life. But correctly reading typology and symbolism is always difficult!!!
I like Calvin's comments on this:

It is indeed certain, that man would not have been able, had he even devoured the whole tree, to enjoy life against the will of God; but God, out of respect to his own institution, connects life with the external sign, till the promise should be taken away from it; for there never was any intrinsic efficacy in the tree; but God made it life-giving, so far as he had sealed his grace to man in the use of it, as, in truths he represents nothing to us with false signs, but always speaks to us, as they say, with effect. In short, God resolved to wrest out of the hands of man that which was the occasion or ground of confidence, lest he should form for himself a vain hope of the perpetuity of the life which he had lost.