Dear Sarah, I am completely re-writing a manuscript that I subbed to you previously (you politely passed). The concept and a few of the original characters remain. My goals are to add more humor and action, make the plot more concise, etc. Would you consider an all-new incarnation if a certain amount of time has passed from my previous submission date?
I think it is fine to resubmit, if the manuscript has changed very extensively (ie, not just tinkering).
Bear in mind our submissions are now all via Query Tracker (see Submissions page of our site), and we are closed to new submissions until January 18.
All good wishes