So, in those use cases, I think that it would be okay to have the question mapped against multiple standards, even if it existed in the question bank, not just in the context of the quiz. The instructor can filter all of their reports and coverage/performance criteria to only the standards that they care about.
The use cases if we map them to an individual quiz have pretty poor usability. Every time I copy a question to a new quiz, I would have to remap it. In the U.S., the publisher would have to create 50 quizzes (actually 49, as one state hasn't adopted standards). Generally speaking, the publishers in the U.S. use a company called Academic Benchmarks for aligning against state standards, and they have a meta-ID layer, which allows them to map the question against all of the state standards by mapping them against just one "meta standard". These are usually distributed through software bundled with the book (the most common is called Exam Soft), but they are localized to a particular state (as is the teacher's edition of the text book). This does remind me that I should add a use case for the import of quizzes from ExamSoft/Respondus/etc, that are mapped against outcomes. It would be good if the API for the questions also brought in the standards (we could make this an option, I suppose). I'd love to hear your thoughts on how to best do this.
I did have another concept that people are asking for on the quiz that is related to this. Several of the people who have been reviewing would like to be able to tag a quiz as a practice quiz or a drill quiz, rather than an actual assessment. Then they would like to be able to partition the performance data based on the type of quiz. (They would use some of the same questions in each, but the drills would be done earlier in the term).