I believe many are unknowingly in misunderstanding concerning the concept that the Body of Christ, the Church, has somehow entered into that which God has for His people Israel. He has always "reserved" (Rom 11:4) Jews out of unbelieving Israelites, to believe in Him, which Scripture refers to as a "remnant" (Isa 10:22 Rom 9:27; 11:5), and to this day they include believing Israelites who comprise the Church with believing Gentiles.
I believe the prophecies of Jer 31:31 and Eze 36:26 collate in Scripture to refer to God's final redemption of unbelieving Israel, who will consist of Israelites who have believed in God but not in Christ. These are those who will be living at the time of the fulfillment of these prophecies, somewhere during the great tribulation or during the Millennium.
There is no support to intend the above prophecies to refer to neither pre-tribulation nor pre-Millennium believing Israelites, because the prophecies design the application to Israelites who do not believe, until after seeing Jesus, and God putting His Spirit in them (as it is now with the Church). This could be the intention of "all Israel shall be saved" (all Israelites alive at that time; not those who’ve died since Adam who have believed God - Rom 11:26).
I believe there will be an even greater distinction in eternity between Israellites whom God saves later and the Church, in that those who are "blessed" (John 20:29 - Church - Israelite and Gentile believers) will be in a parental relationship, with God as their God and Father (John 20:17) and they as His children (Rom 8:16); and the Millennium Israelite (if you will) shall be in a form of theocratic relationship, with Him only as their God, and they His people (Jer 31:33 – a relationship that has always been).
Part of my reason sharing material related to the Scriptural distinctions of unbelieving Israel and the Body is to learn what the Lord shows everyone who fellowship in His Word through their Christian forum postings.