This interpretation has some interesting and, I think, helpful, implications.
What I'm suggesting means that, as one theologian put it, "Paul was not against the law as such - far less against 'good works'! What he aimed his arguments against was the law understood and practiced in such a way as to limit the grace of God, to prevent Gentiles as Gentiles enjoying it in full measure."
This implication shines a lot of light on the book of Acts.
In Acts, Paul does many things that are hard to swallow held next to a traditional Protestant/Lutheran reading of Romans--one which (and I welcome any correction from within those traditions on this point; this has just been my understanding of the popular views) sees Paul as attacking the observance of the law in favor of 'salvation by grace through faith.'
As James remarks to Paul in Acts 21:24, "you yourself also live in observance of the law." This comes in the middle of James's sending Paul to purify himself in the Temple, in hopes of refuting claims in Jerusalem that Paul "teaches all the the Jews who are among the Gentiles to forsake Moses, telling them not to circumcise their children or walk according to our customs." (21:21) This is a scandalous accusation that James and apparently Paul both want to discredit.
More striking, I think, is the conclusion of the Council of Jerusalem in Acts 15. This chapter is crucial for understanding the Biblical teachings on Jewish-Gentile relations in Christ.
The council is called to address the situation of Gentiles converting to "the Way". Some, Pharisees in particular, believe that these Gentiles ought to be circumcised (:5)--receive the sign of covenant membership. The apostles conclude that the Gentiles need not be circumcised, but, in their Apostolic Decree, they write that Gentiles ought to follow four commands: "abstain from the things polluted by idols, and from sexual immorality, and from what has been strangled, and from blood." (:20)
These commands might seem kind of random at first, but they are actually pulled from the book of Leviticus. These are commands given to foreigners 'sojourning in the midst' of Israel. They aren't required to become Jews, as Gentile converts traditionally were, but they remained Gentiles and adhered to these precepts.
The men carrying this letter then traveled with Paul and Barnabas to Antioch.
A Paul who was totally opposed to Old Testament law, whom many like to suppose wrote Romans, simply doesn't mesh with this Paul in Acts.
However, a Paul arguing against, not law observance, but an attitude of exclusivism--'God is for the Jews!'--does fit here.
In fact, the Council of Jerusalem decides precisely in favor of what Paul is arguing for in Romans: salvation is available to the Gentiles as Gentiles. There's no need for them to convert to 'outward' Judaism: "For no one is a Jew who is merely one outwardly, nor is circumcision outward and physical. But a Jew is one inwardly, and circumcision is a matter of the heart, by the Spirit, not by the letter." (2:28-29)
In Romans 4, Paul goes on to draw out how it is that the promise to Abraham may apply to the uncircumcised. (Again, Paul is here arguing against an 'ethnocentric exclusivism': 'Abraham and the promise are not merely for the Jews!')
If we want to understand 'works of the law' in the sort of 'standard' way, where it refers merely to 'works that are supposed to earn salvation', this passage seems to be merely an interesting aside.
But if the 'works of the law' that Paul is attacking is instead 'that which distinguishes one as a Jew', his exposition of Genesis 15 makes perfect sense--indeed, it's critical--right where it is.
'You may have thought that justification comes through Jewishness,' he begins, 'but I'm telling you that justification comes through the promise, and the promise is realized through faith.' Abraham's faith, not his circumcision, is what marks him out as the forefather of the people of God, Jewish or otherwise.
This sort of reading of Romans can have some serious ramifications for our reading of the rest of the New Testament (not least of James). It's also got me convinced that "the fundamental problem with which Paul is wrestling in Romans is not how a person may find acceptance with God; the problem is to work out an understanding of the relationship in Christ between Jews and Gentiles." This is what much of the post-gospels New Testament is about, once we start understanding it in context.
This sort of reading of Romans is also exactly the sort of responsible, informed reading that I think Christians have to be doing of our scriptures. Paul wasn't writing in a vacuum--we need to get to know his context. Jesus wasn't a 21st century westerner--we need to know what environment he was in and speaking to, what his terminology meant to his audiences.
There are a lot of great resources out there to help us along the way. Heck, I can think of five theologians off the top of my head who have lead me by the hand in my (this) understanding of Paul. As much as you can, dig into these studies.
More than anything else, though, and before anything else all of us have here to face our call to read and know the scriptures, and to pray for God the Spirit's leadership and guidance. Study the word, and do it as often as you can. Allow God's Spirit--and whatever tools he has placed at your disposal--to direct you in your interpretation and understanding.