II Corinthians 5:14-15, “For the love of Christ controls us, because we have concluded this: that one died for all, therefore all have died, and he died for all, that those who live would no longer live for themselves but who for themselves for him who for their sake died and was raised.”
We can think about a “for” which is not substitution. I can score a goal for my team, without any idea that I am the only one playing the game. I score the goal for the sake of others on my team, and not only for myself, but that does not mean they do nothing and I do everything. In II Corinthians 5:14-15, it is not the “for” which get us to the idea of substitution. What gets us to substitution is “therefore all died”.
It is a MISTAKE to reference the “died with” to a “faith-union” given by the Holy Spirit. The idea is NOT that Christ died one kind of death and as a result the Holy Spirit selects and unites some to “the church” by using water baptism as a “laver of regeneration”. The idea is NOT that Christ rose again from death and as a result the Holy Spirit “pours the power of Christ into” believers.
The idea of “therefore all died”, the idea of “union with Christ’s death” is NOT that the Holy Spirit becomes the agent of that death, and selects who will be on the team. But in the Torrance/Letham view of “Calvinism”, Christ died to have a team, and there is no freewill, so you don’t get to decide to be on the team, but the Holy Spirit does.
The Romans 6 idea of “died with Christ”, the II Corinthians 5:15 idea of “therefore all died” is that Christ died to propitiate God’s wrath because of ALREADY IMPUTED SINS, and that this death is credited by God to the elect.
The elect do not (and did not) die this kind of death. Their substitute replaced them and died it for them. Christ alone, in both His Deity and His Humanity, by Himself, without the rest of humanity, died this death. Christ the Elect One, without the elect, died this death that God’s law required if the elect were going to one day be justified.