This essay must accompany your discussion, along with any of ]] books on Gospel origins, including his recent on on ]]
WHY dig up solid foundations, why open questions long taken for settled? Much critical and expository work rests squarely on the Q hypothesis, and if the hypothesis loses credit, the nuisance will be great. The books we rely upon to guide our thought about the history of Christ will need to be read with painful and unrelaxing re-interpretation. Nor is it only the effect on past studies that disquiets us. We want an accepted foundation for our present studies, and it seems a grievous thing that we cannot proceed with them until we have re-investigated what was unanimously settled by a previous generation. Is there to be no progress in learning? Now that criticism is a science, are we not to hold any established positions as permanent conquests, from which a fresh generation can make a further advance? Have we always to fight the old battles over again? Minds of high ability and scrupulous integrity were brought to bear on the Q question in the great days of source-criticism. They sifted to the bottom, they counted every syllable, and they agreed in the substance of their findings. Is it likely that we, whose attention is distracted by the questions of our day, can profitably do their work again? And what reason have we to trust our judgement against theirs, if we find ourselves dissenting from their conclusions?
via On Dispensing with Q.
Q does not, in my opinion, qualify itself with the literary innovations and structures of the time. Further, as I pointed out in my book, Matthew would need no other literary source related to Jesus but Mark.