A promise is neither a sacred bond nor an agreement, but something quite different from both. Theologically, the concept of covenant promise (by God) contradicts the concept of covenant as mutual agreement. [David Engelsma, PRTJ 46:1 (Nov 2012): 118]
On the contrary, a promise IS a bond and an agreement. A promise given by party A to party B establishes an agreement whereby Party A promises to do X to Party B, and thus Party B can hold Party A to his promise and ask him to fulfill it. It is a bond precisely because the two parties are now tied in a relationship whereby Party A has obliged himself to honor his word. Agreements are agreements, not necessarily "mutual agreements," which is why "mutual agreements" require the adjective "mutual" to modify the noun "agreements."
Similarly, it is contradictory to assert, on the one hand, that “the covenant of redemption was not a ‘plan B’ to fix the mess Adam made, but the original blueprint for the work of Christ” and, in the same breath, to assert that God’s plan regarding Christ was “to remedy the disastrous results of the first Adam’s failure to fulfill the covenant of works in the garden of Eden and bring humankind to glory” (Ibid.)
Here, Engelsma err in failing to see the difference in view between the historia salutis and the ordo salutis, God's revealed will and His secret will. In God's eternal plan and secret will, Adam was destined to fall, though it was Adam's own fault and doing. But in redemptive history, Adam could in fact merit eternal life through fulfilling the conditions of the Covenant of Work. Therefore, in the outworking of redemptive history, Christ was to "remedy the disastrous results of the first Adam's failure." And that is the whole point of the typology in Romans 5 contrasting Adam and Christ, which is that where Adam failed, Christ succeeded. Christ indeed remedied the disastrous results of the first Adam's failure, which one should have no problem with even if one disputes whether Adam can merit anything.
The authors suppose that they relieve this contradiction by distinguishing eternal benefits from temporal blessings and the heavenly Canaan from the earthly. But the fact remains that on their view the Sinaitic covenant was not wholly an administration of the covenant of grace. (Ibid., 118)
Form is not substance. To claim that there is a formal republication of the Covenant of Works does not mean that the substance of the Sinaitic Covenant is in part of the covenant of works. This is a misrepresentation by Engelsma, who shows no indication that he understands anything regarding Formal Republication.