Where does homework fit into a mastery-based grading system?

As I have worked with schools to implement JumpRope and mastery-based grading, there are certain points of controversy that come up early and often.  Chief among these is, without a doubt, the debate around how to handle homework in a mastery-based grading system.  I'd like to begin a conversation about this topic in hopes that the different opinions can help us all improve our understanding and effective use of the data.  Before I begin, I'd like to first make it clear that JumpRope does not systematically enforce any particular approach.  Rather, the decision is school-based (and sometimes even user-based).

First, my assumptions:

• Teachers and schools using JumpRope agree on some fundamental level that gathering data on what students know is important, and that doing so is different from gathering data on what students have done.
• In general, teachers and schools believe that it is important for students to complete work outside of the school (homework) in order to practice their way to higher levels of mastery/understanding.
• Grades are the primary (or at least the most universal) motivator that educators have at their disposal if the goal is to increase homework participation rates.

With these in mind, I fall rather strongly in the camp which states that homework does not offer robust evidence of mastery (or a lack of mastery).  Rather, the completion of homework speaks more directly to a student's character than to their academic mastery.  As such, I believe homework should be scored on character learning targets exclusively.  To assess academic mastery, robust assessments should be administered at a time during which we can be reasonably certain the students complete the work themselves.  With this approach, the data that we gather remains true to the goal of collecting data on what students know as opposed to manipulating numbers with the goal of motivating students (a larger topic that I'll reserve for another post).  In order for this approach to work, however, a few things need to be true:

• Students need to have a pretty good understanding of mastery-based grading
• There needs to be some respect for the "character grade" or "habits of work grade."  This can either be achieved by including character scores when calculating final grades or by otherwise incenting a high character score (with rewards, dean's lists, sports eligibility, etc.)
• Teachers need to be consistent in this practice and in the message they send to students.

I've seen this work before, but it takes some time and effort.  Who else has thoughts?