One of my teachers implemented a system like this. What they ended up doing was making it so that you had to score a (effectively) 9/10 on major assignments to pass the class (minor assignments were graded on completion), but had an infinite number of revisions with which to get this grade with feedback being provided each time you tried. Pretty much everyone passed, with more work required from some than from others. The only issue it ran into was with the final paper, where you (realistically) only had time to receive and make one to two revisions before the end of the semester and the deadline to submit grades.