Pro/Rel would make me interested in the MLS again. It gives everyone something to play for and it forces owners to try to win. Too many owners in the US are only trying to make money and don't care about winning. And that's the way it is in all sports, not just soccer. Force teams to try to win, rather than signing 40 year old David Beckham's just to sell jerseys.
I would gladly help fill up a 10,000 seat soccer specific stadium to help my local team get promoted or avoid relegation, and maybe even pull a Leicester.