Brilliant (er, well...) idea for fall composition course

I'm thinking of trying this approach:

Workshop-intensive (alternating full-class workshopping and small-group peer review)

During "instructor at the head of the class" weeks, a combination of the following:

• One day of assigned work as scheduled on the syllabus
• One day in which students choose the topic, depending on their performance on their previous papers (e.g., "We really want more work on sentence structure"; "Can we talk some more about introductions?"; etc.)
• One day of multiple small group activities, in which students may participate as they see fit & the instructor supervises (e.g., one group revises their papers for the next assignment; one group works with active and passive voice; one group evaluates secondary sources for their final project)

I'm sure that this isn't particularly original, but I wanted to experiment with something more student-driven.  Comments? Suggestions? Objections?