[Mariner]

Make the starting pitcher go 5 full innings.

Limit relievers to 3 per game.

And NO mid-inning pitching changes.

Allow variance for legitimate injuries. If you come out early, 15 day disabled list.

That would shave at least 30 mins from the average game.

[IndyTiger]

Shorten the season to 154 games, with at least six double-headers. If teams are whining about the gate, make the double-headers day - night games, with a separate gate for each game. Shorten the playoffs so only the World Series is best of seven games, other playoff series are best of five games.

This would knock off about two or three weeks from the length of the season.