MLB
Play 144 games, get rid of divisions and wild cards. AL and NL, best of 7 LCS, WS best of 7. Pitch clock and batter stays in box*, rigid enforcement. (* limited exceptions).
NBA
Play 62 games: 4 divisions, get rid of conferences for playoffs seeding purposes, no East/West. Let high seeds pick their opponents until final of course.
NFL
16 games, no divisions, 2 conferences. Let high seed pick playoff opponent.
CFB, accepting the current 4 team playoff.
let top seed pick their opponent. Semis are a home game.
NHL, cut off 10 games, maybe 20. Go back to Wales and Campbell Conferences, with Division names (Adams and Patrick, Norris and Smythe)