Experimenting the best way to assess the coursework

Other than giving short quizzes and test, throughout the years I have also tried to devise various not-so-conventional ways to assess the students as a continuous effort to optimise the quality of the assessment. Below are some examples of my attempts.
Open book quiz was administered right after the lecture on a chapter is completed. Usually open book quiz means the solutions are not directly available in the text book. Open book quiz free students from the almost compulsory practice of rote memorisation. On the other hand, despite having the textbook available for reference, students found themselves being challenged very hard in these quizzes, and were forced to think harder. However, this attempt did not work very well. Except a few students who could think out the box, most students who were average in their learning and thinking model failed to answer well these challenging questions. The overall coursework grade for the class was so poor that I never give open book quiz again in other classes.
The “Sample Questions by Students” initiative: Students were invited to design some samples of formatted objective questions based on the topics covered in the course. These objective questions were required certain criteria, especially, they must be original (no cut-and-paste from existing resources), conceptually correct, creative, and “interesting”. Copy cat or boring questions were filtered and rejected. Once accepted, the designer of the questions would be given bonus points for the coursework. The accepted “designed questions” were edited or corrected by me, and then stored in a question bank which, like all other course-related material, was accessible online. I also promised the students to adopt some of the selected designed questions in the examination as an incentive. This initiative promoted a good sense of participation in the teaching and learning process. In addition, to design an original objective question demands thorough knowledge about the subject matter. Creating sensible questions to someone deepen the level of understanding on a particular concept in the questioner, a wonderful and interesting way to make a student become learned. A student who attempted to design a question inevitably must also get involved in an in-depth learning process. Overall, in that attempt 143 designed questions were received. Not every ones found this initiative inviting, only about less than 20% students sent in their questions, of which many are copy-cat. But those who are enthusiastic found the initiative an interesting learning experience. One thing for sure, the initiative has successfully aroused the sense of participation in the teaching of the course, at least among those who submitted. Now, the down side of the initiative. To filter through and edit tons of submitted questions, of which many were copy cat or simply nonsensical, from a large class (or around 300 students) was an exhaustive task. The expansive cost of time and effort consumed had demotivated me to exercise it again in other semesters. Nevertheless, it is otherwise an interesting assessment method which I would still like to implement in smaller classes, with the condition that extra assistance from tutors becomes available.