This would completely change the game, and could also result in some more late-game comebacks.
Instead of an onside kick, which is a pretty tough task, teams would just have to make a 15-yard gain in order to keep the ball after a score. Granted, that's also a tough task, but it might be a little easier than recovering an onside kick.
Another thing to consider: What about coaches like Bill Belichick, who has supreme confidence in his offense, and is willing to take chances? Would we see him "go for it" 10 times every game, under these new rules? Sure, it would risk giving the other team great field position, but with that offense, it might be worth taking the shot, if it can get you 3 or 4 scores in a row.
What do you think about this new proposal?