My thoughts on the matter. Don't allow pitchers to walk around the mound during at bats and don't let batter adjust their s*** continually. If a manager comes out to challenge it must be done instantly, no waiting for confirmation -> give them 2 challenges per game. They can still come ask for confirmation for things but not a challenge if they did not signal right away. Have a dedicated two man team for every game for replay analysis. No more huge waits, if they see a challenge they can start reviewing instantly before headsets are even on.
As far as the season goes I'd say you could shorten the schedule 14 games (to 148 per season) and increase the first wild card series to a best of 3. I know a lot of Canadian's (and I think it's stupid) want to see more play off teams. I think a lot of other sports do it wrong. If 50% of the league is good enough for the post season you should have two leagues with the champion teams in each league in one league and the s*** teams in another. People complain about how long the baseball season is but f***, hockey runs from October to June, it's insane that people don't complain about that.