I've had this idea for a few years -
Cut pre season to 3 games. Game 1 would be as normal, game 2 would be the "dress rehearsal" and game 3 would be the all backup and bubble guys (as the 4th pre season game is now). Then after game 3, every team has 2 full weeks to the start of the season
Expand the regular season to 17 games. This keeps all 20 games while shortening pre season and only adding 1 regular season game. Add 2 teams from each conference to the playoffs for a total of 14 teams.
Benefits of this : less injuries from a shortened pre season. More revenue due to 17th game and 2 more teams in playoffs. Happier players because they will recieve more pay from added game and its the same amount of games as before (including pre season)