I offer another invitation to rethink the WinFS problem before it's too late. For example, what if you were to drop the idea of a schema?
Instead of trying to squeeze a database as you know it into a file system, how could you make a database more dynamic?
Slice the database in a different dimension. Throw it in a linear accelerator, smash the database particles, and see what you get.
Think "outside the box" instead of just trimming one box to fit inside another.