It seems to me that the answer is a) that we don't like using the word 'heresy' since W. Bauer ... blah blah blah ...; b) that it is being done with respect to LXX at the moment; c) that we did have commentaries based on a single manuscript tradition for three hundred years (and most of them aren't very interesting on the detailed exegetical material); d) that it would be very interesting to have a series of textual commentaries on important manuscripts - treating them seriously as an artifact and representation of the text in its/their own time; BUT that e) if you want to comment on Paul you need to comment on the text you think Paul originally wrote. You might take P46 as your starting point and then vary from it, but effectively then you are still commenting on an eclectic text. The more disciplined you were in commenting on the manuscript itself, the less sure you would be that you are commenting on Paul.
I have this insane idea for biblical studies. Why is it when scholars write a commentary on a NT book that they inevitably use either UBS4 or NA27? The fact is that no extant manuscript conforms to the text of UBS4 or NA27 so they are writing a commentary on a manuscript that does not physically exist.
Let me qualify that: (1) I believe that it is worthwhile to comb the various witnesses and try to establish what is probably the original autographs; (2) I'm not advocating the superiority of any one particular textual witness like the Western Text or anything like that. But why doesn't someone take, say, the earliest manuscript on Galatians (p46, ca. 200 I think) and write a commentary on that manuscript and argue in the footnotes passages where they think other readings are to be preferred.
I put this forward because, although I believe in the eclectic approach, at the end of the day there will always be an element of doubt as to our ability to reconstruct the original autographs with any certainty. Alternatively, p46 is a real manuscript not an imagined one, and the question that can be asked is to what degree does p.46 legitimately represent the original autograph. Is using a real manuscript (as opposed to a hypothetical one) as a template for the text of a commentary an act of textual critical heresy; or am I onto something?
The great commentaries of the past, thinking of say Lightfoot on Galatians (probably the greatest commentary in the history of NT scholarship), understood that an important part of the commentator's job is to establish (and publish) a critical text alongside the commentary. NT scholars today generally relinquish this job to NA27 and Metzger's Commentary (perhaps thinking that by-and-large the text critical task is complete, or else that the whole field is a bit too complicated) and invest their time and energy in different aspects of the commentators task.
So I'd be all in favour of a series of textual commentaries. Publishers would love it; RAE points for everyone; they would be permanent contributions to scholarship (if done well); helpful for Wirkungsgeschichte; honouring to the memory of the scribes; full of detailed pictures and charts. But I think they would be a lot of work. Sign me up for a little fragment.
What do the rest of you silent co-bloggers think?