End tanking by implementing a two-tiered promotion/relegation system. I would use around 40 teams including MLB and about 10 teams that are currently AAA. The worst records in MLB go down to the lower league and the best from the lower league get promoted every year. Less revenue sharing in the lower league, so it costs the owners $$ if they don't field a competitive team.
More talent is needed for a league of that size, so minor league pay needs to be greatly increased along with significant additional investment in youth and HS baseball.
Every team has to play an international series every year.
Robo balls/strikes and a strict pitch clock. And by strict I mean strict. Going over the pitch clock needs to be a play that can be challenged and reviewed by the opponent.
Scoreboard shows a "gameday" interface which will improve engagement with casual fans at the stadium.
Create a set of standards for the 'ideal' baseball game -- runs, K, BB, stolen bases, doubles, triples, HR per game. Adjust rules after every season to aim for those metrics. Need to avoid the current situation where drastic changes are needed to get things back to 'normal' baseball.
In extra innings, teams have to play with one less defender every inning. 8 men in the field in the 10th inning, 7 in the 11th inning, etc.
Foul bunt on two strikes is not a strikeout until the 2nd or 3rd attempt.