I totally support what Josh said, but I would also want to add this:
IMO the 4-minute time alottment for each move is massive. I know that accidents happen: you may have lost your internet connection, ran out of battery, got an important phone call, you even may have had to stop your kid from hurting itself -- sure. In many instances, you have the time to forewarn the opponent of your impending idleness before it happens. Sometimes you don't. Tough luck... but that's an infinitesimal number of cases, I believe. What you will normally come up against is a ruffian who, seeing they are bound to lose, will just leave the game rather than resign honourably. If anything, I'd be more happy to see the rating punishment for forfeiting on time be very tangibly higher than a normal ratings' loss resulting from a loss.