Question Bank looks like a great idea but how you are looking to group them ? I would prefer to be grouped according to chapter and tagged for associated target section. In this way, while reading the chapters from difficulty level 0 to 2 (top-down), the question bank will include the ones which were also targeted to the previous sections and randomizes the questions to test the thorough revision of the chapter.
We should focus on collection of questions first and then we can eventually build up the system later on. We can collect questions in a sophisticated data structure in some kind of database to make this happen. Another task would be adding already deployed quizzes to that database. The database can be made up of JSON, YML or even using online tools like Google Sheets, Google Form etc.