Not very anglican this, but hey.
In reading Barth's "Theology of the Reformed Confessions" it has been helpful to have the contrasting attitudes to public Church documents of the Catholics, Lutherans and the Reformed laid out with some of their consequences.
Barth is less than optimistic about the current likelihood of the Reformed Church of his day getting down to writing any new confession (The book consists of lectures from 1923) although he thinks any significantly reenvigorated Reformed Church should get round to this task.
The Scripture Principle is for Barth a defining idea characteristic of the Reformed. It occurs to me, however, that even this would need to be rethought in any new confession, not inorder to remove or undermine it but to preserve it.
Part of the problem I forsee is that when the appeal was made to Scripture during the Reformation, it was made with some implicit theological assumptions. Defining what these are is not easy. They would include, I think, a doctrine of God, his goodness and oneness, his history of care for Israel; a recognition of Scripture as set apart by God for his purposes; an understanding of humanity - that the authors of Scripture and its modern readers stand, fundamentally, in the same relationship to this one God. Although this probably risks opening up a can of worms, we could call these things a 'rule of faith'.
The reason all these things become significant is because of the treatment of Scripture during the Enlightenment and beyond. The appeal to go back to the Scriptures of any new confessional movement is potentially thwarted by the recognition that modern readers (reading without some of the above assumptions) have returned to the Scriptures generally speaking they have found only a plurality of voices, confusion and moral ambiguity.
So, in conclusion, is it possible to hold onto a simple Scripture principle? If it is possible to ennumerate the theological assumptions of the Reformers and would we want to share them? Either way, what would be ours and from where would we get them? From Scripture?
Now, perhaps I could be accused at this point by a wagging finger, the person behind which would complain that these readers are simply unrepentant sinners, not reliant on divine grace, etc. and that the answer to our hermeneutical question is one of 'prayerful' reading. The irony is, such a position contains within itself innumerable theological understandings and indeed relationships to God. I think piety is an essential element of any answer here, but the very idea brings with it the question 'what kind of piety?' and 'who is this God I am worshipping?'.
I would like to find a way of laying out these tensions and questions in a stable manner ... or, at least, if the instability is fundamental to the task, be in a position to recognise this to be the case.