So far I've shared that annihilation of the soul is an impossibility because of the nature of the image of God in which mankind is made. I've also said that manipulation or control of the image of God by fiat would so mar it as to render it no longer the image of God. I've also stated concerning repentance that "through the Gospel and the conviction of the Holy Spirit we have our opportunity." That, however, raises the question about whether or not the lack of opportunity might negate the need for the Gospel and conviction. Let's explore.
God does not, I don't know that he can, make a soul (in his image) live in accord with him if that soul doesn't want to in its own right. Adam and Eve were good according to God, without sin within, but they were not willing to submit. Jesus faced serious temptation, especially in Gethsemane, but was willing to submit. In the prototypical models of humanity, it seems, the principle is that the image of God must willingly agree and submit if there is to be agreement and submission at all.
God is not without tools to accomplish his purposes with the image of God: he can convict, he can persuade, he can woo, and he certainly can suggest. Indeed, he must do all that and more if any are to be saved, but putting puppet strings upon the image of God is just something he will not do over the long run. The result would not be the image of God if he did. Therefore, repentance is absolutely essential to living in God's image after death.
Let's say there is a unevangelized pagan somewhere at sometime who looked upon the witness of creation and realized that God was behind it. That pagan reasoned that he must acknowledge his Maker and submit to him. Would not that pagan be like Abram in Ur, or even perhaps even something akin to Naaman? Would that pagan thereby find mercy and grace in God, and be included in Christ? No, he would not for very good reasons.
At very best, and by his own reckoning, he would serve God according to his own devices; would be dependent upon his own works to maintain his status with God; would have to fashion his own religion to serve God (is that not intrinsically idolatrous?). What is unclear about the scriptures' judgment about the efficacy of any of those actions? If works do not justify a Jew, who has the law from God's mouth, how are they going to justify a pagan who has conjured his law through his best intuition? He may get a few things right, but by no means would be justified before the Lord. He may know there's a Creator, what he needs to know is the Savior.
In the case of Abram, and all of the OT patriarchs (Noah, Isaac, Jacob, Moses, even Samuel) what made the difference for them was the visitation of God. Whether by direct appearance, or through the Holy Spirit revealing, or by the word of God being heard (or read), God must make the difference if a person to a have saving faith (which was true for even Naaman and the Ninevites in Jonah's day). This is just not something people come to on their own, even looking at the witness of creation. Some may object saying that's unfair or unloving (subjective), but what's more important is whether or not it's true (objective).
I say, we must trust God to abide by the word Jesus spoke (John 6:37-47 ESV):
All that the Father gives me will come to me, and whoever comes to me I will never cast out. For I have come down from heaven, not to do my own will but the will of him who sent me. And this is the will of him who sent me, that I should lose nothing of all that he has given me, but raise it up on the last day. For this is the will of my Father, that everyone who looks on the Son and believes in him should have eternal life, and I will raise him up on the last day."
So the Jews grumbled about him, because he said, "I am the bread that came down from heaven." They said, "Is not this Jesus, the son of Joseph, whose father and mother we know? How does he now say, 'I have come down from heaven'?" Jesus answered them, "Do not grumble among yourselves. No one can come to me unless the Father who sent me draws him. And I will raise him up on the last day. It is written in the Prophets, 'And they will all be taught by God.' Everyone who has heard and learned from the Father comes to me—not that anyone has seen the Father except he who is from God; he has seen the Father. Truly, truly, I say to you, whoever believes has eternal life.Jesus, in this passage, tells us how saving gets done. In a nutshell, salvation is the work of Christ, the benefit of which is bestowed on all who believe in him. That belief is specific and personal, for it results in the saved coming to Christ, looking to Christ, and believing in Christ. To those who grumbled about his claim to be the divine means of salvation, Jesus defended his exclusivity and necessity and dismissed their objections by saying that if a person was learning from God, he would come to Christ.
Where, then, is the hope for the noble savage, if indeed, such a beast exists? I've shown that the development of saving faith requires the visitation of God. If that is so, why would God visit and direct a heathen to someone or something other than Christ? If one postulates there is another path to salvation than saving faith, the burden of proof is upon him. I cannot find any clue of such in the scriptures.