I think they should just give each team a possession and make it sudden death after that (or end it if a team is winning after 1 possession), at least for playoff games. Maybe leave the regular season alone
There are other ways to make changes though.
- You could keep the same rule, but only end the game if they score 8 points instead of just the 6 for the TD. That would force a team to make a decision on going for 2 and the automatic win or kicking the extra point and letting the other team get the ball. that would add a great deal of intrigue
- You could make a rule that each team possesses the ball, but the 2nd team only gets as much time as the first team actually uses (if they score, if they don't score there is no time restriction). So if a team returns the kick for a TD, the 2nd team only gets the 15 seconds or whatever. If the 1st team gets a long first play and ends up in FG range after 30 seconds, they could elect to kick the FG (and give the other team like 35 seconds) or they could try for the TD and take more time off the clock giving the other team more time. That would add some intrigue and strategy.
- they could do something similar to the college system. I'm not a huge fan of that, but maybe instead of the 25, they start at the 40 or something. Abbreviates the game, but gives both teams an actual shot at offense.