Brian, if you don't have time to work on it in the next little while, maybe you could post your partial patch in case someone else wants to work on it?  Might be a good project for someone on the mentoring list.

Unless someone sees a clever way to implement both with the same mechanism, parameterizing test cases should probably be a separate issue.  Doing it via subclassing is straightforward, which also argues for a separate issue, since an 'is this worth it' discussion should be done separately for that feature.