Remove the Manuscript from the Submission Process

When editors buy from a proposal—which is most of the time—they presume that the manuscript has yet to be written, which is true most of the time. I believe, therefore, that it is better not to disabuse them of this notion. Better, I believe, to remove the manuscript from the submission process altogether and to submit a proposal for your book even if it is already written. In addition to giving the editor less to turn down, you will probably want to rework the manuscript anyway based on the editorial feedback you have received from the proposal.