In my reading of A. Andrew Das' Paul and the Jews, I appreciated Das' discussion on pages 142-148 about the concept of blamelessness in Second Temple Judaism. To be honest, I could not tell whether Das was agreeing or disagreeing with E.P. Sanders, but he still presented important data.
E.P. Sanders' argument is that Paul was not trying to refute a Jewish notion that one needed to keep the law perfectly to be saved, for Judaism did not have such a concept. Rather, for Sanders, Second Temple and rabbinic Judaism thought that only the deliberately rebellious among the Jews would be excluded from salvation, as well as recognized provisions of atonement for Jews who sinned. But advocates of the New Perspective (which Sanders holds) also lean heavily on Paul's claim in Philippians 3:6 that, prior to his conversion to Christ, he was blameless with respect to the requirements of the law. New Perspectivists appeal to that verse to refute the idea that Paul before his conversion to Christ was burdened by his inability to keep the law.
Regarding whether or not Second Temple Judaism required perfect obedience of the law, Das argues that prominent strands of it did. Jubilees and Philo advocate perfect obedience towards the law as well as elevate biblical heroes as people who achieved this (though Philo qualifies Noah's perfection by saying Noah was only perfect compared to the people of his time). The Dead Sea Scrolls also exhort members to follow the law perfectly. At the same time, the Dead Sea Scrolls acknowledge that everyone sins. On page 147, Das quotes a beautiful statement by Sanders about the Qumran documents: "from the point of view of the halakah [legal strictures], one is required to walk perfectly. From the point of view of the individual in prayer or devotional moments, he is unable to walk perfectly and must be given perfection by way of God's grace."
Das also appears to question whether blamelessness means absolute perfection. On page 147, he states: "Biblical figures were often characterized as 'blameless' even when the biblical text admitted their sins (2 Chr 15:17 [cf. 2 Chr 16's catalog of sins]; Luke 1:6, 18-20). Paul could admonish his own audience, while it struggled against sin, to be blameless (Phil 2:15; see also 1 Thess 3:13; 5:23; and 1 Cor 1:8). So blamelessness with respect to the Law ought to be distinguished from perfect obedience...Although Paul describes his prior status as blameless, he nowhere says that he was without sin as a Pharisee."
Another interesting point that Das makes on page 147 is that Paul was accused by some of his peers of nullifying God's grace in holding that the Mosaic law was not a path to salvation, for the Jews "associated the Law with God's grace." That, for Das, is why Paul denies in Galatians 2:21 that he nullifies the grace of God.
I do not know how much of what I wrote represents Das' position, and how much is his summary of Sanders. But Das does talk about complex issues: What is perfection?; Was Paul aware that the law had gracious provisions?; etc.