For instance mere belief in Jesus or recognizing his Lordship is not sufficient to be a saint beause even the devil would meet that definition. Likewise, it cannot be only those in the church triumphant or Paul used the term inappropriately when writing to living saints in this letters that compose nearly half the New Testament. It is not even just a few select individuals canonized by the Church, or again Paul was wrong in the way he used the term.
The simplest usage that I can think of is to recognize that the New Testament word most commonly translated as “saint” is the word
hagios, which is also translated not just as “saint” but as “holy”. So, saints are nothing more and nothing less than “holy people”. Now, how do we become holy. We become holy when God makes us holy. We become holy when we are purged of our sins and made righeous before God. In once sense none of us are therefore likely to be holy into we have died and entered heaven, for our sinful nature seems to continually remind us that we are not truly as holy and righteous on this earth as we are called to be. Yet, on the other hand, the God who calls things that are not as though they are, does declare us to be justified, cleansed of sin and imputed with righteousness.
Thus it is not we who call ourselves saints, but God who declares our holiness. And who are we to call God a liar.
So it is in this context that I see Paul refer to living persons, many of them still imperfect keepers practioners of righteousness, as saints. And it is not Paul alone who speaks of those in the church militant thusly, so does Jude, Ananias, and Luke. And as you pointed out above, it is also used by John in reference to saints not only in heaven, but those saints on earth who continue to offer prayers (Rev. 5:8) and who have war waged against on earth them by the beast (Rev. 13:7).
Protestants who read thiesepassages will not deny the reality of intercession of and for the saints any more than Catholics who read these passages will deny the universal applicabilty of the term “saint” to all persons who are declared holy by God, both the living and the dead.
This communion of saints is a oneness we share by the work of the Holy Spirit that convicts of sins and leads us into all righteousness. (Notice that its confession is part of the third article of the Apostles’ Creed which spells out the work of the Holy Spirit.) Having been claimed by Christ, we are made one not only with him, but also with one another just as Jesus prayed for in John 17. That is the essence of our communion. And as the CCC expresses it, “it reaches [both backward and forward] into eternity, embracing all who are being purified to enter the blessed vision and all who are already rejoicing in the beholding of God’s glory.”**
**I do note that the context in which the CCC made this statement was with regard to our communion with those who have preceeded us in death. Yet, logic demands that if we have communion with them in a communion of saints, then they must also be having communion with us. Thus we have both the dead and the living both joined to one another in a communion of the saints. It is not just those who have gone before us who experience this, we experience it with them. Therefore, we must also be part of that one and the same communion for they do not have communion with us apart from us also participating in it along with them And this makes perfect sense, as it is all who are being purified, and though the author of the sentence may have been thinkin of purgatory, it is no less true that we who are among the living, if we are in Christ, are also in the process of being purified even before death (Acts 15:9, 2 Corinthians 7:1, Titus 2:14, James 4:8, 1 Peter 1:22, 1 John 1:9, and 1 John 3:3).
Thus it is that sainthood is not something that we actual attain, but rather, sainthood (holiness) is a state into which in grace calls us. As W.E. Vine stated it in his Expository Dictionary of New Testament Words:
Hagios] expresses something more and higher than hieros, sacred, outwardly associated with God; … something more thansemnos, worthy, honourable; …something more than hagnos, pure, free from defilement. Hagios is … more comprehensive… It is characteristically godlikeness.
This godlikeness is what it means to be a Christian, one reflecting the image of God and the person of Christ in one’s life. When we become a Christian, a person claimed by Christ, whether we like it or not we become holy persons, persons set aside for God’s purposes in our lives. We are sanctified, working out his holy and perfect will in our lives. Though we may not be worthy of the title, we nontheless are transformed by God into people that the New Testament authors callled saints, each and everyone of us.