I think it would be cool if you had like your own page (or some other alternative) where essentially you could pick subjects (and perhaps also specific topics in those subjects) for regular review.
For example I might want to pick just the classes I'm currently taking and topics we have covered so far in my class. Then get 5 (or user selected value) random review questions (can use your multiple choice banks you already have) from the areas I've picked. Could perhaps set it up to send a daily notification reminder. This would allow regular study through out the semester in a somewhat fun way.
Could even use it long term for all classes already completed to have some random questions a day or week as we enter practice to stay knowledgeable. I'd pay for that.
Further you could even add arbitrary rewards like special stickers or avatars or something for days in a row or completing certain subjects (not necessary but Duolingo has something like that and it's a nice little hit of dopamine).
And perhaps one more feature could be like some modern learning software, where if you get a certain areas questions right all the time you get less of those questions. Forces you to get ones you need to work on (this part wouldn't be absolutely necessary).