I saw an idea someone had that I think made more sense than the 4th and 20 rule. The issues he pointed out were that on a 4th and 20, a minor (or incorrect) holding call gives the "kicking" team a new possession and the defense is forced to defend the entire field.
His suggestion was this. Instead of having a 4th and 20 from your own 40, you get one play from the opposing team's 15 yard line. If you get into the endzone on that play, you get the ball on your own 35. If you don't, the defense gets the ball on their own 40. That way, the defense isn't stuck trying to defend over half the field, and if there is a penalty, the ball gets respotted, and you have to try again.