A few ideas, none of which I expect to get any traction whatsoever
Keep the DH/AL no DH/NL it gives us something to talk about even when the teams are made up entirely of guys we have never heard of.
Go with a designated runner who can be used once a game with no penalty.(The player runs, returns to the bench and the original player stays in the lineup and the designated runner is still available as a sub) The catch is that the opposing team gets to choose which player becomes the runner.
Put Herb Washington into the HOF as a pioneer.
Get rid of the participation medal all star game. If your team doesn't have anyone good enough they need a better farm system or better coaches or better front office, or all of the above.
Eliminate the hitters backdrop. sell the seats, or if the players MUST have music to get out and play, a bandstand with a live band. If the wall is more than 420 at the deepest the bandstand are must be there , and is IN PLAY.
Bring back stuff like the lederhosen wearing people who slid down into a beer mug if the Brewers hit a HR. Maybe make them mandatory? Tampa can use bikini girls (Or whoever, it's 2017 after all, but bikini girls would get my vote)
Bring back Promotions like bat night, ball night, nickel beer night.....especially if they're combined - I do love a promo gone awry, especially if it's a PR disaster.
No indoor ball. It's MLB, not whiffleball or something cooked up for gym class.
Do make new stadiums in coastal cities on a huge turntable. That way no matter the time of the game the field can be rotated to take advantage of the ocean breezes. Teams with weak pitching might opt for "wind always blowing in" ones with stronger hitters might go for "wind always blowing out" No penalty for teams caught rotating the place between innings.