You allow "in voto" for charity as a relative necessity of means, but you deny that faith in revealed truth can likewise be allowed "in voto".
You know very well that if a person holds the 4 explicitly, that he holds the Incarnation, Resurrection, and the rest, "in voto". There is nothing philosophically or theologically against holding the Trinity and Incarnation "in voto" likewise because of that trusting act of the will.
Here is a quote from "God and Man: Lectures on Dogmatic Theology" (1915)
Notice it says "all theologians" in regard to a country not having received the Gospel. That signifies that it is indeed a truth that, by a relative necessity of means, a human can obtain the divine virtue of faith, which would "in voto" contain that of the Trinity and Incarnation.
Take note, that the "distinction" above is one of invincible ignorance or not.
You also know both St. Alphonsus and St. Thomas take the opposite opinion. So unanimity is not so much.
There are certain articles of faith that can be held implicitly in the confession of more necessary articles.
Now, the Holy Office has said that the Trinity and Incarnation are articles necessary by a necessity of means, and therefore cannot be held implicitly. In this matter we must follow the Magisterium and insofar as theologians go, if they are divided, I choose the ones that agree more with the magisterial and Curial decisions, hence St. Alphonsus and St. Thomas.
Moreover, the supernatural act of faith cannot be conjured up by the will, it can only be willingly received and submitted to.
Now, if God chooses to reveal that he is a rewarder and punisher to a person in invincible ignorance, why would he not reveal himself as the incarnate son?
Job himself was a gentile in good faith, and Christ manifested himself as the redeemer of the world to Job. "For I know that my redeemer Liveth and I will stand with him on that day, and in my flesh I will see God."
Again as Paul says in Hebrews, "God spoke in various ways in times past, but in these latter days he has revealed himself through his son."
And as Christ says, "My sheep hear my voice."
Therefore I cannot believe that those who accept the gift of faith will remain ignorant of Christ and will not be able to identify the voice of the shepherd of their souls. "My Sheep know me and I give them eternal life."