Regular emails with questions would certainly be possible with snail mail. But the fundamental problem with all of those suggestions is that only reviewers who

Regular emails with questions would certainly be possible with snail mail. But the fundamental problem with all of those suggestions is that only reviewers who really wanted to take a lot of time and care with reviewing would take advantage of them, and since there number of reviewers like that is vanishingly small, it wouldn't be worth the effort to establish the necessary systems.