So can someone prove to me that the ecclesiology that most trads hold to is definitively not Tridentine ecclesiology but is really only Vatican ii ecclesiology?  I’ve seen ladislaus assert this a lot but I haven’t yet seen it conclusively proven.  But that does seem to be the core issue

Tridentine ecclesiology emphasized the visibility of the Church, teaching that the Catholic Church is a visible society ... against the Protestant heresies to the contrary.  St. Robert Bellarmine emphasized this aspect of the Church, almost to a fault.  Nevertheless, it was considered that only those were members of the Church who could be visibly identified as such through their reception of the Sacraments, profession of the true faith, and subjection to the Holy Father.  There were a couple of great articles referenced in the one sedevacantism thread (where PC2 and Don Paolo were having it out), one from Msgr. Fenton and another by a Father Lawlor.  Both gave great detailed histories of Traditional Catholic ecclesiology.

Vatican II ecclesiology, however, has more of a concentric circle look to it, where the Church subsists in the Catholic Church and the core of the Church is the Catholic Church proper, but then people have various degree of invisible belonging to this Church, where they are invisibly in the Church while being visibly outside.

Now, if you hold that non-Catholics can be saved, you must hold that they are in the Church, since there can be no salvation outside the Church.  So here you have a Church that consists of both actual Catholics, visibly united, as well as those who are invisibly united to and within the Church.  Which of these two ecclesiologies does this more resemble?

Back on the BoD topic.

A FSSPX priest confirmed that the Fraternity believes that BoD is, in principle possible, albeit truly in borderline circuмstances and the contingency is, for all practical purposes, extremely unlikely.

He explained also that anything is possible for God and, therefore, he can save any soul at his pleasure. Even further removed from BoD.

However, he added, it would be foolish for anyone to rely on the off chance that God would save us, un-deservingly, and we should strive for salvation by adhering to correct catechism.

But used in this way, it's not true that anything is possible for God.

I’m sure that if you got down to the nuts and bolts of the OP’s question, most of the trad organization’s leaders would say that the deceased person who was a member of the false religion would NOT be saved by or in that false religion, but in spite of it. The person who was “saved” would actually have to be somehow incorporated into the Church and thus have died inside the Church, for outside of Her no one can be saved. That is dogma, period. Also, it must be remembered that the individual in question must have, at the bare minimum, knowledge of the Trinity, the Incarnation, and the Redemption.

Of the number of the elect and predestined, even those who have led the very worst kind of life are led to repentance through the goodness of God, through whose patience they were not taken from this life in the commission of crimes; in order to show them and their co-heirs the depth of evil from which the grace of God delivers man. Not one of. them perishes, regardless of his age at death; never be it said that a man predestined to life would be permitted to end his life without the sacrament of the Mediator. Because of these men, our Lord says: 'This is the will of him who sent me, the Father, that I should lose nothing of what he has given me.'11 The other mortals, not of this number, who are of the same mass as these, but have been made vessels of wrath, arc born for their advantage. God creates none of them rashly or fortuitously, and He also knows what good may be made from them, since He works good in the very gift of human nature in them, and through them He adorns the order of the present world. He leads none of them to the wholesome and spiritual repentance by which a man in Christ is reconciled to God, whether His patience in their regard be more generous or not unequal. Therefore, though all men, of the same mass of perdition and condemnation, unrepentant according to the hardness of their heart, treasure up wrath to themselves on the day of wrath when each will be repaid according to his works, God through His merciful goodness leads some of them to repentance, and according to his judgment does not lead others. Our Lord says He has the power to lead and draw men: 'No men can come to me unless the Father who sent me draw him.'12