This is my understanding of James 1:15 which I find more consistent with the rest of scripture than what you are suggesting.
Then after desire has conceived, it gives birth to sin, and sin, when it is full grown, gives birth to death.
What death is James referring to? If he is talking generally and applying it to anyone at any time, he is effectively repeating what God said in the beginning. "Sin and you die" (Gen.2:17)
We know that Adam did not die (completely) on that day he ate. He remained physically alive, he was not completely abandoned for the Lord walked into the garden next day to speak with him. We understand Adam died spiritually. But according to the word of God, Adam should have been
totally abandoned by God, physically, spiritually and his soul, (the complete man) forsaken by God. The Father could "suspend" the complete consequences of Adam's sin without compromising His integrity (holiness) because of the Christ to come, planned before the foundation of the world. When Christ came he did die "in the day" just as Adam should have. For three hours on the Cross while He was paying for the full consequences of our sin he was forsaken by God. This is something no man will ever experience. Please take special note of this and keep it in mind.
No man will ever experience what it is like to be fully forsaken by God (die) because of his sin. The death Christ died on the Cross is the death Adam should have died in the garden but didn't.
If James is referring to believers in the verse above (and I believe he is) then the whatever death he speaks of is "covered" in the death of Christ, spiritual, physical and of the soul. However we know believers die physically, we see it everyday. In practical terms the warning James is giving us (believers) has application in regards to physical death. This corresponds to Paul's statement in Corinthians.
That is why many among you are weak and sick, and a number of you have fallen asleep. 1Cor.11:30
Their sin has brought God's judgment upon them and they have died physically yet they are
in Christ and because He has died, these people will live.
It also corresponds with John.
If anyone sees his brother commit a sin that does not lead to death, he should pray and God will give him life. I refer to those whose sin does not lead to death. There is a sin that leads to death. I am not saying that he should pray about that. 1Jn.5:16
Any believer who willfully continues to practice their sin without regard for their salvation will not mock the Lord. He will take them out of this life (physical death) so that His name is not blasphemed. Now sometimes He does it quickly and they die young and sometimes he does it slowly and they hang around for awhile. Invariably, those brothers become a test for us who are growing up in the Lord.
Now if James is referring to spiritual death as you are suggesting, the practical implication is completely unmanageable. It would mean every time any of us sins, we would die spiritually. If we are not spiritually alive the word of God becomes as foolishness to us. We would need to have the Gospel presented over and over again. Only those spiritually alive can be taught of God. Only those who are spiritually alive have the capacity to understand the word of God. Most of us commit sins which we are completely unaware of. The word of God would have to say ...
"Unless a man be born again and again and again and again and" .... on it would go for every sin we would commit.
The reason we don't die spiritually every time we commit a sin is because we are
in Christ. He died that death on our behalf once and for all.
So why is it, if Christ died for us spiritually and physically, we don't die spiritually when we sin yet die physically whether we sin or not? It is because the sin nature resides in the flesh and until we get our resurrection bodies the sin nature remains in the members of our body.
For in my inner being I delight in God's law; 23but I see another law at work in the members of my body, waging war against the law of my mind and making me a prisoner of the law of sin at work within my members. 24What a wretched man I am! Who will rescue me from this body of death? 25Thanks be to Godthrough Jesus Christ our Lord! So then, I myself in my mind am a slave to God's law, but in the sinful nature a slave to the law of sin. Rom.7:22 - 25
That law, working in our bodies, keep us as slaves to sin. That law never stops operating, not until we die or the resurrection, which ever comes first. Whether we live under it's law or whether we live under the law of the Spirit is an ongoing choice but it is a choice only made possible if we believe in Christ. For only in Christ does the option to live the new life (governed by the law of the Spirit) exist.
Believe it or not? Yes, they are being transformed but they are not being transformed in their soul (thinking). In terms of a man's spirit, transformation is not applicable. One is either dead or alive. No transformation takes place. You can't be "partly" spiritual. (that would make you a spiritual zombie. there is no such thing
) The other transformation left is physical, but as I said before, that is in the resurrection. That won't occur until God says "time's up" (so to speak). We
all still wait for that time.
This is why we don't "see" their transformation. This is why we are inclined to think they are not saved. But the Lord can see the beginning from the end.
So what happens to a believer who refuses to be transformed in his soul while on this earth when the resurrection comes and he stands before Christ?
If any man builds on this foundation using gold, silver, costly stones, wood, hay or straw, 13his work will be shown for what it is, because the Day will bring it to light. It will be revealed with fire, and the fire will test the quality of each man's work. 14If what he has built survives, he will receive his reward. 15If it is burned up, he will suffer loss; he himself will be saved, but only as one escaping through the flames. 1Cor.3:12-15
What does he lose? The majority of his spiritual blessings that have been placed in Christ. (Eph.1:3) He still gets his spiritual body and his place in God's Kingdom and the obvious benefits that would come from that. But the difference bewteen his life in eternity and someone who has grown and matured, is like the difference between a peasant in an earthly knigdom and the life of a royal advisor and confidante to the King.
Our work is our faith. Our faith is the word of God made alive in our soul, made alive by our willingness to trust in it's truth. Whatever is not of faith (truth) is burnt up and destroyed but if one believes that Jesus is the Saviour, even if they know no more than this, they have at least one truth in their soul and therefore are saved. No-one believes on Christ if they think he can't or won't save them. I doubt any one of us understood in full what we were being saved from when we believed in Christ. We knew our lives were wrong. Whether we understood why or how they were wrong is inconsequential. We believed and therefore are saved.
peace