In my plan, each student is interviewed at least once. Ideally more than once by the same teacher, so the teacher can get to know them a little better, spot areas where the student needs more help, etc.

There's still a scaling problem, but I think it makes the ~200 student classes we have now more feasible than 100% autograding. I also like the other commenter's suggestion of coming back to interview certain students each time, if they need it.