Option #3 is unfairly presented. There is no reason a language couldn't implicitly box every type, but automatically create efficient specializations for (some

Option #3 is unfairly presented. There is no reason a language couldn't implicitly box every type, but automatically create efficient specializations for (some of) the types actually used. You can have your cake and eat it too. Of course, it's not easy to write such static optimizations. But it is, in principle, possible, and the sort of thing you only need write once.