From Lack of Plight to Solution?

I have a question that I'm hoping a lurking Federal Vision proponent can clear up for me:

If neither the Adamic nor Mosaic arrangements were legal covenants of works, then to which covenant is the covenant of grace the antithesis?

Our Reformed dogmaticians have been divided about whether the Old (Mosaic) Covenant was essentially gracious or legal, with divines at the Westminster Assembly holding to both positions. But even those who insisted that the Mosaic covenant was simply an administration of the covenant of grace clearly saw the Adamic covenant as being a covenant of works.

Thus, irrespective of whether the Law/Gospel antithesis was couched in Moses/Christ or Adam/Christ language, there was a Law/Gospel antithesis.

But if both the Edenic and Sinaitic dispensations were essentially gracious (because the creatureliness of [fallen and unfallen] man precludes his earning anything from his Maker), then where's the law, where's the bad news, where's the question to which Jesus is the answer, the problem to which he is the solution?

With all our talk of "relevance" in the Church today, one would think that if our cardinal message fails to identify a crisis to solve, then perhaps we're more irrelevant than we ever dared imagine.