I think this is a legitimate approach to commenting on the confessions, because the confessions themselves, somewhere in the Formula of Concord (anyone remember where?), argue that the holy writings of Martin Luther are also held in high regard, not quite as high as the confessions themselves (or Scripture) but certainly up there.
And if any text is important in the overall theology and confession of Luther, certainly his essay on The Freedom of a Christian is way up there, together with, for example, The Bondage of the Will, the Galatians commentaries, and the Babylonian Captivity, to name a few.
Luther has a central dialectical argument he makes in this essay, and it is the kind of thing worth meditating on for days and days and praying over. It's amazing. A nice summary of it is on page 71 of the Tranvik translation:
"Insofar as a Christian is free, no works are necessary. Insofar as a Christina is a servant, all kinds of works are done."
Luther opens the work with this set out as two statements, side by side, in the first page of his essay:
A Christian is lord of all, completely free of everything.
A Christian is a servant, completely attentive to the needs of all.
Another way of stating this dialectic has to do with who we live in and where our lives are directed. In terms of our life towards God, in Christ it is completely free because it has been justified by faith. In terms of our life towards the neighbor, we are servants of all.
Or as Luther has it, "As Christians we do not live in ourselves but in Christ and the neighbor. Otherwise we are not Christian. As Christians we live in Christ through faith and in the neighbor through love." (88)
So much of our confusion as Christians stems from mixing up these two items and conflating them. Holding the two in tension in the dialectic is important, and part of the work of Christian theology. Spending some time with Luther's little book (in Tranvik's wonderfully fresh translation) has reminded me, if I needed reminding, of why I continue to be a Lutheran theologian.