I like baseball, but if I were the Baseball Commissioner with absolute powers, I would do the following:
1) Shorten the regular season by at least 20-30 games. It's just too freaking long. Starts too soon, ends too late. To make the cut, perhaps I would get rid of interleague play, go back to the way it was in the old days. Made the World Series more special, when it was the only time all season the two leagues would meet.
2) Use some of the time gained in step #1 to expand the playoffs. 6 teams per league oughtta do it.
3) Hard salary cap and hard salary floor. No more Yankees and Red Sox signing every top free agent that becomes available and spending more than half the league combined. No more Royals and Pirates spending peanuts on salaries and pocketing their revenue-sharing checks.
4) Instant replay available to be used for all close calls (except for calling balls and strikes, which will remain the umpire's judgment). Any potential home-run, fair-foul call, safe-out call, plays at the plate, and so on are eligible to be reviewed. There's no reason nowadays to have to accept blatantly erroneous calls anymore. In order to limit the number of replay delays this would introduce into each game, I would limit replays to a couple times per game by going with a "coach's challenge" system, as in the NFL.
and this last idea is a bit more "out there" but I think it has potential
5) Borrow a page from basketball and institute a "pitch clock" (maybe 30 seconds). Like the "shot clock" in basketball, this will serve to keep the game moving. If the pitcher doesn't deliver a pitch when the pitch clock expires, it's counted as an automatic ball and the clock resets. If the batter is out of the batter's box when the clock expires, it's an automatic strike instead.