I am happy to have contributed a little to the preparation of Wallace's argument (in private correspondence) about the inconcistency on the part of Ehrman (and others), when he appeals to intrinsic evidence, and at the same time takes a completely agnostic position as to what a certain author wrote. In fact, I discussed this issue with Ehrman on a textual criticism discussion group in 2008 (here). Ehrman fully realized the problem as he responded:
Now, if someone can explain to me the logic of appealing to an author's style when you don't think you can get back to his words (hence his style), I'll eat my Westcott and Hort!
Consequently, in the new edition of his The Orthodox Corruption of Scripture (recently released), he has a brief discussion of the "resulting theoretical problem," i.e., the apparent contradiction of his own reconstruction of an early form of the text, and his claim that there is no way of getting to an original (pp. 350-52). There he states:
At the same time, I have not observed other critics wrestling with the issue; instead they continue to use intrinsic probabilities even while admitting that we have no access to an authorical text. I belive that is a problem, but I also believe it has a theoretical solution.
Then Ehrman proposes that although we are reconstructing an "author" with verbal, stylistic, literary and theological predilections, and although "recognizing them allows us to decide which readings go back to his imaginary pen and which were later creations of scribes," we must at the same time acknowledge that this author is not a tangible human being of the past.
I actually agree with Ehrman – this is the bottomline of my own reply to him (and actually in accordance with the theoretical basis for the Coherence Based Genealogical Method, which seeks to reconstruct something more than the archetype of the tradition, but less than the authorial text – the term used is "the initial text"). So the question then is how far removed is our reconstructed author's text from the historical author's text? In my discussion with Ehrman I further suggested:
As I said, the simplest theory is that the initial text is the autograph (we do not know); the more complicated theory, the less is intrinsic evidence worth .... In practice, we assume that the text we reconstruct approximates towards the author's text.
In sum, other text-critics have indeed wrestled with the problem, even directly in discussion with Ehrman. I also discuss the issue in my essay "The Implications of Textual Criticism for Understanding the ‘Original Text’" in Mark and Matthew I. Comparative Readings: Understanding the Earliest Gospels in their First Century Settings. Edited by Eve-Marie Becker and Anders Runesson (WUNT I 271; Tübingen: Mohr Siebeck, 2011). There is much to say about this problem. I have found Peter Shillingsburg's works very helpful in this area. Perhaps I will post something on that in the future.
Finally, "the theoretical problem" is of course mainly a problem for those who are utterly pessimistic about reaching the initial text ("the more complicated theory, the less is intrinsic evidence worth").