Here's a suggestion. Keep all the rules exactly the same except for the following.
First team to score 4 or more points wins. Game over. You can still kick a field goal, but you didn't win yet. You are up 3 and would still need another 3 to get the sudden death win. If the 15 minutes elapses and you are up because of the 3, good for your team. You win. The only downfall to this suggestion is there will be a few more ties during the season, but at least it gives the team that is driving in first an incentive to score a touchdown rather than a field goal.
This is the best overtime change idea i'ver ever heard!! I like it! Cause all teams play so safe in overtime knowing they just need a FG and never even try for the TD. This would change that and make overtime much more interesting :aktion033