You are giving the hard core Covenant theology view here...
You do realise many, dispy such as myself, would not see the scriptures in the same light?
As we do NOT recognize either Covenant between the trinity, not that of Works as in the bible!
Then you are wrong! There is no other covenant of grace than that which was made between the Persons of the Trinity and that is precisely why it is called "the blood of THE EVERLASTING covenant."
There never has been ANOTHER GOSPEL than that preached by all the Prophetes - Acts 10:43/26:22-23/Heb. 4:2
There never has been ANOTHER WAY of salvation than through Christ and the "blood of the EVERLASTING covenant" - Mt. 7:14/Jn. 14:6/Acts 4:12 given under heaven and among men.
There never has been ANOTHER salvation.
Israel as a nation is the "elect" ETHNIC nation who will be saved by the same gospel, same Savior, same way when Christ returns (Rom. 11:25-32) by the very same covenant of grace. There is no other covenant of Grace and there are no other parties involved in that covenant than the Trinune Persons of the Godhead.