Well if you want to guarantee that the playoffs aren't shrunken, there is no valid argument. I interpreted this to mean that if in one league there's a sub .500 in the playoffs and in the other league there's a .500 or better team out of the playoffs, then that better team should swap leagues and join the playoffs. Mathematically, it does not bear out. I do not have the time to do the math tonight, but with around 15 teams in a conference/league, it is possible for there to be only 3 or 4 .500 or better teams.
So what are you going to do, cancel the NFL Wild Card Weekend or first round of the NBA Playoffs outright? Or are you just cool with cancelling a round of the playoffs in the NBA and NFL if that's what it takes?