Quiz

Hello
My original question was supposed to be - how to enable negative grading for attempted but unanswered quiz with essay activity (auto-submitted at due date)? It is still valid, but I describe my problem little more detailed.

I have many Essay Activities prepared for my students. They have different difficulty level, so every one have it's max grade. I would like give a hint about question subject, and let the student decide to enrol or skip the particular one. If he decide to risk, a question will be presented for him. But if he won't answer, or only try to pretend to answer, I would like to assign negative grade for that attempt.

My idea is like that:
Create many courses, single activity type, one for each question. Then in each of them create single essay quiz - I fought I will be able to manually assign negative grade here. Then if user see the description of the course (hint for the quiz question) he decide to enrol or not. If he won't - ok, he gains nothing. If he enroll, he will be presented the question and will be supposed to answer the quiz essay question and gains its profits. If he passes after revealing question (course enrol and access to quiz) he will be punished with negative grade. Any better idea? To make it possible, I'll need answer to my question from top of this post.
Moodle 3.+

Thanks and regards
Karol