Completely disagree. While I love pro/rel for pro sports, that is the quickest way to kill professional domestic soccer in the United States. While there's better money abroad, we need to have players here be able to make an ok living so people will want to pursue that as a career. If you institute pro/rel, teams will collapse when they're relagated because they won't have the fan support. Unlike other sports in the U.S., I don't think many teams in the MLS have the fan support necessary to support them if they are relegated.
Would it work at leagues below MLS? I still don't think so because any fan bases they do have would collapse when they were relegated.
Finally, if you're talking about youth leagues (which maybe you are because of the comments about the players and parents), I still don't think pro/rel is a great idea. First, how is that going to generate money so that the players aren't funding them themselves? Second, one issue at least several years ago was that the youth teams cared too much about winning and not enough about development. Pro/Rel would only exacerbate that issue.
I think to help improve our soccer athletes here in the United States there needs to be more low cost leagues (in addition to other changes that people smarter than me will come up with). I don't know where the funding comes from for that, but I don't think Pro/Rel helps, maybe the USSF? Second, I think the MLS teams need to continue to grow/improve their academies. I think this is where the development will happen because the focus can actually be on development and not on winning
MLS is currently trying to bastardize the European model. They wanted to create top-level clubs, and now try to backfill the talent generators that the established European clubs already have. Europe is littered with clubs, not much different than we all have near our homes in all major markets around the US. The only difference is, some of these clubs have senior teams that are Barca, Manu U, Real Madrid, while others are the white dragons or whatever name they have. All of them play a roll in the system, the small clubs, that don't have major senior teams, develop local talent, that talent then is typically bought by larger clubs, as the talent progresses through the system, each time it is bought a little of that money trickles down through the system, and the local club gets it piece of the pie for developing that talent. Parents aren't on the hook for paying $1,500/year plus to get their kid to soccer. The local kids that never will be professionals have small clubs to play for. I am sure there is some pay for play in Europe, but for the most part, there is not. This system is used throughout the rest of the world, the MLS doesn't want this system in place in the US, as they feel they will lose their talent, as well as the money generated by being exclusive. Well guess what, Europe has been doing this for so long they hold the financial advantage. And until the US produces consistent top-level talent the MLS is never going to be the EPL, Bundesliga, La Liga or any other top league in Europe, and quite likely never will. But to just ignore how the rest of the world develops talent is crazy, and if it continues we will consistently under develop talent in the USA.
In my opinion, the US should set a plan in motion to start pro/rel on the lowest levels, up to USL and NASL. MLS should stop all expansion, It then should say MLS is the premier league. Then a plan should be set in motion to open up MLS to pro/rel in 5 to 10 years. Yes, it is possible that NY, LA, Chicago, Houston will have more than one top-level team. But I think there are creative ways to combat that. The US is approx the same size in population the largest Euro league countries combined. So why not break the US into regions, each with their own top-tier senior league. Then you could have a North American Champions league with those regions, along with Mexico, and possibly Canada.
Right now US kids have to make a choice when they are 14 or 15, move to Europe to get the best training, or stay in the US and know they will likely never make the most of their talent. It is tough on a family to ship their kid to another country at that age, In Europe, this is a rare thing. Messi came to Barca at 14, but most top-level talent grows up in its home country, only to make the leap to the big boys once it is truly ready. The US does not have this mid-tier level to help the development of the 14, 15, 16, 17, and 18 years old, and then the MLS wants the 18,19,20-year-old to go to college, where they can't learn their trade more than the NCAA allows and it stunts their growth.
And don't tell me there isn't money for this in the US, there certainly is, fan bases would grow organically with the local clubs, people support minor league baseball, NCAA football, NCAA basketball and a ton of other sports. This model can be funded, and it will produce talent.