The Body of Christ is composed of the Elect that have been Baptized in the holy Ghost period. These are considered the Spiritual Jews (Chosen of God).
The knowing of the truth is what sets us free, and the truth is that if one is chosen then that one is of the elect and a member of the Body.
But you do not have a choice. If you are the elect of God he will open your eyes to see the truth of his plan in his own good time. If you are not to be a member of the elect group you will stay blinded to the truth of that plan no matter how many times a week you go to church, or tithe, or preach it is Gods choice not anyone elses. This is the Sovereignty of God. Similar to Jacob have I loved and Esau have I hated before they were born to show us it is by HIS choice. He will accomplish HIS WILL on the earth as he does in Heaven and who is going to stop him?
As far as the elect are concerned I would quote Romans 11:29 "For the gifts and calling of God are WITHOUT REPENTANCE." That is to say he will not change his mind about who he has called.
I think you may be placing to much emphasis on anyones need to go tell them in the Churches what they teach is wrong. We know, but it's not up to us to go make a scene within their houses of worship, besides you'd just get thrown out, I know it's happened to me many times. When the Father wants to draw one of his own out of those houses he will provide them with revelation of truth then when they have digested that truth and seen that it is contradictory to their groups teachings they will "COME OUT OF HER MY PEOPLE", but until that time they will remain in a state of infancy if they truly are elect.
I refer again to the 7 letters to the 7 churches in REVELATION. There are things that must be experienced within the Church community by us all in order to tell the difference between good solid doctrine and a flat out lie. The deeds and doctrine of the Nicolaitans, Jezebels teachings, the doctrine of Balaam, etc.. and in the overcoming of these errors in what they do or preach has a reward associated with each. This is a personal issue between the Lord and his elect and will happen when he chooses for it to happen. Rev 3:19 "As many as I love, I rebuke and chasten(correct); be zealous(for the truth) and repent." Of what you have done before you knew these truths. And especially if you knew and continued to do what he has told you not to do.
Those that do come out of her are rewarded with the HIDDEN MANNA, this is for them not those that have not come out or won't.
Those that do overcome are allowed to eat from the TREE OF LIFE, that tree contains no knowledge of good and evil just allows one to see who is really causing the world to move as it does and kills self will (carnal mind).
In saying all that I still enjoying posting here but the main focus for us all is to align with the New Covenant as well as we can and be patient for the changes that mature us be it day by day or week by week. We all grow according to HIS plan not ours. I would quote Jesus here: John 5:26-27 " For as the Father hath life in himself; so hath he given to the Son to have life in himself. And hath GIVEN HIM AUTHORITY TO EXECUTE JUDGEMENT also, because he is the Son of man."
Remember when I broke down Judgement according to the Greeks. Judgement- a separation, involving a time of crisis, which is a way of knowing. Since he has been given authority to do this I think I will try harder to not get in the way for his judgement is far superior to mine. But I do know how you feel when you discover a new truth you just can't help yourself you want to tell the world, but the world cannot receive it because it is BLINDED.
He also speaks to the fact that there are those among the Churches that claim to be spiritual Jews (The elect) but are not. Rev 3:9, 2:2, 2:9. They are there on purpose to derail you from achieving to a higher inheritance in the Lord. If you overcome what has been placed in your path then you are rewarded accordingly. The rewards spoken of in the 7 letters still apply to ALL of the ELECT today as they did nearly 2000 years ago. Find yourself within the Church that the letter is written to and seek to overcome that issue and be rewarded. Then move on to the next.