This is a horrible idea and will never happen, but hypothetically what if this indeed was a new rule for this year. If you were the head coach, would you ever punt? If so, at what yard line would you draw the line? I know it all depends on the game situation, the time left and so forth, but generally speaking, what yard line would you draw the line?
Off the top of my head, you wouldn't want to put the other team automatically in field goal range, but there is a chance you would make the 1st down on 4th too, so you have to factor that in. Tough call.
Let's say it's a tie game early in the 4th quarter, you're on your own 10 yd line with 4th and inches. That would be VERY difficult to call IMO. Punting would automatically put the other team ahead by 1.