I've started exploring Coderunner, and it works great with quizzes. But often I want assignment semantics, not quiz semantics. For example, allowing late submissions is trivial with Assignments but cumbersome for Quizzes. And Assignments send messages when feedback is available.
Ideally there'd be a way to just make Quizzes have Assignment-type semantics. But that seems hard. Slightly easier but still probably hard: making an Assignment Submission plugin that can host several Quiz questions. (This would be nice in general, for letting students answer each part of a multi-part assignment individually, for example.) Maybe easier than that, but less useful, would be an Assignment Submission plugin that only hosts coderunner.