If it works, and it's a plugin, not mangling core, it's good enough, IMHO.
Some teachers are quite insistent that they need time-per-question and a general setting for that (expected answering time) in question definition UI and in quiz-editing page. There are some strong opinions. Perhaps we need to discuss again some months from now. But I see an starting point.
Whatever the code, once built, refactoring as plugin or the reverse, move from plugin to core is a lot easier with working functional code than just starting from scratch.