Help designing college course grading system

eMoander

Background:
My wife is teaching a calculus course at a community college and would like to better incentivize the students to do homework and quizzes, since in traditional grading systems they are weighted so low relative to midterms and finals that most students just ignore them (and then tend to do poorly on the midterms and finals. There is another teacher at the college that has been trying to bring more gaming-based ideas to his classes, which she thinks would be a good idea given that the majority of students are gamers now, but she spends essentially no time playing games. Hence, she has approached me as her resident expert to help design a fun and incentivizing grading system for the class. I have put together a plan, but I'm sure the numbers aren't perfect and it would probably be pretty easy to break the system, so I am posting it here to both identify/fix flaws in my system as well as to hopefully solicit even better ideas.

Constraints:
- There are 9 quizzes, 2 midterms, 1 final. There are a larger number of homework assignments, but in general everything up to a quiz is merged into one score, so there are effectively 9 homework grades, generated in parallel to the quizzes.
- You can't pass the class if you fail the final, or either midterm
- You should be able to pass the class if you ace the final and do zero additional work
(There are probably some other constraints she mentioned that I'm not remembering, I'll respond to questions in the thread)

Her initial idea:
For every homework that is successfully completed, the student gets a token
A midterm would be worth 200 points, spending a token makes it worth 400 points. If you spend a token and get >80%, the midterm is then worth 600 points
(Note she hadn't thought it through much more than this, but the problems I see is the tokens really aren't worth much relative to the final and you would have a lot of wasted tokens; ie once you do 2 homework assignments, you have one token for each midterm and there's no point in doing any more homework).

My current best idea:

                        Reward                   Max Points
Activity   Grade    Points  Tokens  # per class  w/o tokens  Multiplier cap
Homework    <70%      0       0         9            0             0
            >70%      0       1			

Quiz        <70%      0      -1         9        9000 (11%)       5X
            >70%   %*1000     0			

Midterm     <70%     FAIL     0         2        20000 (25%)      5X
           70-90%  %*10000    0			
            >90%   %*10000    3	
	
Final       <70%     FAIL     0         1        50000 (64%)      None
           70-90%  %*50000    0			
            >90%   %*50000    3			

Pass the class = 50,000 ; A = 70,000
Top scores go on a leaderboard that continues from year to year, they get to choose what name (instructor has veto)
Total class score goes on a leaderboard against other classes using the same grading system (live updates during the quarter?), also continues year to year

Token Rules:
Retake a quiz or midterm (any score) = -2 tokens (only if you can pay; max once per test; tokens spent prior still apply to the score)
Fail a quiz = -1 token (can’t go negative)
Fail a midterm or final = fail class (unless retaken)
Can spend tokens at any point before a test is taken for a score multiplier:

Tokens     1  2  3  4  5  6  7   8   9   10  11  12  13  14  15  16  17  18
Multiplier 2  3  4  5  7  9  12  15  18  21  24  27  30  33  37  41  45  50

*exception: tokens earned for high scores on the final apply retroactively

Key benefits:
• There is a gambling element to tokens, so you want to spend some early on quizzes where you are confident, but that cuts into your max later. Risk of wasting tokens on a bad score should make them study harder!
• Failing quizzes has a significant direct impact (not sure if we want to allow going negative or not)
• There is a big risk in not having 2 tokens available when taking a midterm as you can fail instantly
• A large chunk of tokens are only available for scoring very well on the midterms, so only those who were going to be getting A’s anyways are really competing on the leaderboard

Some alternative ideas:
• Can you retake the final? Maybe it costs 5 tokens instead of 2. Might cause some people to hold back a couple tokens to be safe, while sacrificing their top scores. Also it pushes borderline students to get tokens since they will be very afraid of the final and opportunity to retake will be big for them.
• Have a cap on tokens that can be hoarded at any one time (say 8 or so), thereby forcing students to have to spend them earlier. Gets rid of the obvious strategy of just saving all your tokens til the end of the class.

Note that in this system, you can score way above what is required for an A (the flipside is it may be too easy to get an A if you can pass; I don't see many people getting a C in this system), so the drive to do homework is driven by both the ability to retake tests if you screw up and to compete with the fellow students.

Anyways, I'd appreciate all comments and suggestions, positive and negative. Would you be more motivated if you took a class using this grading system? What would make it better? Are you aware of any similar systems that have worked well in other settings? I'm happy to explain my reasoning behind some of the above points as well if anyone is interested.

One other big concern my wife had is the competition may be great for motivating male students, but it may not work for female students. I was hoping the alternative use of tokens for retaking tests would be provide some incentive there, but I'd love to hear other opinions on how well it may or may not work for females.

Thanks for reading!