Alex, in light of the snips from comments by various modern popes, is there truly any wonder that there is such little enthusiasm among the Orthodox for reunion with Rome?
[Let us] talk about how Catholic ecclesiology relates to Catholic soteriology. I will make a few comments in that direction, and if it indeed interests you, we can take it up further. Also, you asked what I think, but both you and I should be primarily interested in what the Church teaches. I try to reflect the Church's teaching in what I post. Now, I may misunderstand it, and then someone with greater knowledge should correct me, but I try to avoid personal speculation even if I have some such.You should know that two principles overrule any of the discussion: the sovereign ability of Christ to have extraordinary mercy on anyone based on the condition of the man's heart; and our inability, and direct commandment not to attempt, to judge souls. All we can do is see how the revealed Word of God applies and reach conclusions based on outward signs and behaviors. The operative word for that process is "ordinary". For example, we say that baptism is necessary for salvation "ordinarily": that is, we have revealed doctrine according to which baptism is necessary. What happens in exceptional circumstance when baptism is desired but unavailable is not ordinary process of salvation, and all we can do is hope and speculate.
I should also probably mention that we do not use the word "saved" (or "justified") in the same sense as most Protestants (who routinely talk about "being saved" as an event in their life). We are saved, or not, at the end of our lives. Baptism puts us on the road to salvation, and our whole life we work toward it under grace. So, when a Protestant hears that there is no salvation outside of the Catholic Church he thinks that he has just been damned to hell, while in fact he has been told that we don't know if he will be saved or not when his hour of death and judgement comes. Conversely, when we say that sacramental absolution and the Eucharist save, we mean that one who received these sacraments has the certainty to be saved if he commits no future sins till he dies.
With this said... There is but one visible Church into which all Christians are baptized. That is the Catholic Church: everyone: a Protestant, an Orthodox, a Roman Catohlic, so long as he is validly baptized, is at that point Catholic and he is justified at that point.
"Validly" here means by water, in the name of the three persons of the Holy Trinity, and with serious intention of Christian sponsors. If the baptisee is of adult sound mind, he should repent of his sins. The method -- sprinkling, immersion, etc. is not important, and the age of the baptisee is not important. Christ -- not the baptisee and his state of mind -- is Who makes baptism work.
If one is baptized and immediately afterwards dies, he goes to heaven. "Baptism now saves you", teaches St. Peter. Of course, in most cases he goes on living at makes various decisions. He might commit personal sin. If he is privileged to receive Catholic or Orthodox sacraments he should go to confession and strengthen himself with the Holy Eucharist and penitential work, and so, gradually, defeat sin, stay on the road to sanctity and die justified, "making his calling and election secure" (2 Peter 1:2-11).
But what if he is not Catholic or Orthodox (simplifying things let's call him Protestant)? Then his ability to repair sin is gravely limited: he can repent of it but the supernatural cleansing of a sacramental absolution is not there, and the supernatural strengthening of the Eucharist is not there either. At this point he relies on the mercy of Christ; his eventual salvation is in peril. The road to salvation on which his Baptism placed him is barely stepped upon. Further, typically he is separated from the Catholic Church not only by instances of personal sin, but also habitually -- he never considered himself Catholic, his faith does not include the faith in the Chruch or her sacraments. His Catholic baptism wears off quickly and he is no longer in the Church.
Now, he still can do much to advance his sanctification: he can follow the strong moral code his pastor will teach him, and he can get sanctified through the study and love of the Holy Scripture. He can do much with these extraordinary means of salvation, and put us lukewarm Catholics to shame with his love for the Lord and heroic virtues. One thing, however is necessary for us to say that his salvation is not far: a desire to find and unite with the One Holy Apostolic Catholic Church that Christ set up on the rock of Peter (Mt. 16:16-19).
What of his culpability for leaving the Church? It is only there if it was an act of informed will. If someone grew up in a Protestant environment, and his Protestant culture lead him to his Protestant community of faith, he is not culpable. If on the other hand he spent his time insulting the Church or her saints, then such Protestant condemns himself and destroys the kernel of truth that his branch of Christianity taught him.
What of a non-baptized? Well, the same principle applies: did he follow the Divine Law to the extent known to him? Did he wish to know God by name? Did he wish to unite with what he does not know enough to call Catholic Church? On the other hand, did he reject Christ? Fight a war on His Church? Hate Christians for their faith?
As you can see, this doctrine is at the same time hopeful and Catholic-centered. The salvation comes from nowhere but the Catholic Church, yet paths people take to that Church may be very circuitious.