Law, Gospel, and Apostasy

In his essay entitled "Why the Law-Gospel Paradigm is Flawed" Rich Lusk writes:

"... [T]he Mosaic law was simply the gospel in pre-Christian form. Or, to put it another way, the New Covenant is just the Old Covenant in mature, glorified form. The Torah is an earlier chapter in the same glorious Christ-centered story of grace and blessing."

And in his essay "The Tenses of Justification" he argues:

"... [W]orks do not justify in their own right since they can never withstand the scrutiny of God’s inspection. But we will not be justified without them either. They are not merely evidential (e.g., proof of our faith), but even causal or instrumental ("means") in our final salvation. Faith is the sole instrument of initial justification, but faith comes to be perfected by good works" (emphasis mine).

If "the Mosaic law is just the gospel in pre-Christian form" as our brother argues, then that would seem to have some pretty important ramifications for New Covenant living, not the least of which is the seemingly unconfessional idea that works play a "causal" role in our final justification.

As we begin to look at the (very real) danger of apostasy, my initial question is:

How may the notion that New Covenant saints are in essentially the same covenantal condition as the saints of Old Covenant times—particularly with respect to our need to keep the law to be justified—affect how we think about the possibility of, and remedy for, apostasy?