MLB - I’m missing the point on why they think they need to tinker with the current alignment. What does having two 15 team leagues do for the sport? Then it starts to look like Big East basketball. I think the current three division alignment is fine with a wild card is fine. If they wanted to add a second wild card, that may workable. I think baseball attendance is at an all time high - I’d be really careful with messing with that. They need to resolve some ownership issues, not screw with the schedule.
If baseball wants to do something, they should eliminate the designated hitter.
NFL - they’re taking a real risk with the weather. It was marginally acceptable to hold games in Buffalo and Green Bay when the winters were relatively warm; now they’re talking that winters are colder, which means frozen games in northern cities. If there’s cold weather in April for baseball, they can postpone. It’s really hard to postpone a football game - logistics are a nightmare. If they add two games, they should expand the rosters because these guys are going to be maimed in an 18 game regular season plus three or four playoff games.
NBA - already has an 82 game elimination/play in tournament. Mess with it all they want and it will (a) still be too long and (b) be largely uninteresting until the playoffs. Interestingly, when I first started watching the NBA, there were 8 teams and 6 made the playoffs - the regular season eliminated 2 teams and 75% of the teams made the playoffs.
NHL - sort of the same comments as the NBA. IIRC, when the NHL had six teams, four made the playoffs - once again play the regular season to eliminate two teams. The experiment with NHL teams in southern cities has had mixed results. The fan base is in Canada and the northern US. Demographics infer that the fan base with shrink in the northern US - a real problem for the NHL.