For approximately 25 yrs (Yes—I am that old)many years now, I have refereed only non-anonymously (as mentioned in a previous MO question). It has not been uncommon that the authors of a paper I recommended with reservation—or, especially those I rejected—to write me directly, and we subsequently engage in an online (but off-journal) dialog to improve their paper, often for another venue. Almost uniformly these dialogs have been productively positive. Easy for me to say, because of course I hold all the power strings.
Nevertheless, what Igor B. suggests seems to me would be a significant improvement on the current system. My experience with the more one-sided communication I have experienced predicts that it could work well.