Can God's dealings with Israel be brought into the Church, which is His Body?
No. In God's economies, that which He was doing with Israel cannot be brought into the Church, which is His Body. Israel and the Church are two separate economies and must be kept sorted, not mixed, because the Body of Christ is uniquely Pauline and distinct from Israel's law economy.
Les teaches that in the economies of God, you cannot take that which He was doing with Israel and bring it into the Church which is His Body. Israel and the Church are two separate economies; they cannot be mixed but must be kept sorted. The positional term "in Christ" is uniquely the Body of Christ, and the Jew under the law economy is never spoken of as being in Christ. Likewise, tribulation saints cannot be put back into the Body. This distinction is necessary to understand the resurrection order: after the first fruits at Christ's resurrection, those in Christ will be resurrected at His coming.