@Ewitkows1 beat me to the Relegation point. Even with that, the larger markets would never be relegated (akin to Man U and Chelsea in the EPL). I would like to see some form of it, but it would be tough in the US culture.
Give minor league players a better paycheck. SI Article
Football thrives because of exposure on TV. Provide better streaming options where I don't have to pay a boat load of money to watch my local team. I know it is a little different, but I can't watch any games without subscribing?
Either go with all DH or no DH. Then, get rid of the American and National Leagues. Or, if you have relegation, have one be the Premier league and the other is the First division.
Force fans to pay a fee when they are constantly getting up DURING THE INNING or DURING A PITCH to do... whatever. I'm there to watch the game, not play elevator getting up and down multiple times an inning. [disclaimer] This one is tongue in cheek [/disclaimer]