Like the idea of student self-evaluation and/or peer-evaluation as your primary grading mechanism but want to give students a bit more structure for doing that work? Consider contract grading.
The concept of contract grading is that the professor describes in the syllabus the amount of work that students need to complete and the timetable for completing it that will earn a particular grade; students then choose which grade they would like to sign a contract for, and they commit to doing the appropriate amount of work during the semester.
Asao Inoue has used contract grading to highlight the role of labor in a student’s learning experience, making student labor visible and at the center of a course in a way designed to promote social justice.
Cathy Davidson has made peer-grading (on a specs grading-style pass/fail scale) central to her use of contract grading, so that the individual student choice through the contract and academic community through the sharing of teaching and evaluation work are both prioritized.