First off, know that it will never happen.
BUT! If MLS were to have promotion/relegation, what could/would/should it look like?
Most other leagues around the world simply have a season, and the team with the best record at the end of the season is crowned champion. A few teams with the worst records are relegated to a “lower division” league and replaced by promoted teams who finished at the top of the lower division’s league. Simple.
The United States is different. Rather than crowning a season champion, teams must qualify for a “winner take all” elimination tournament: playoffs. The U.S. does not have a promotion/relegation system partly because of playoffs. With a playoff system, the question “Who is the best team worthy of promotion?” is never fully answered. It could be the teams with the best record, or it could be the team that gets hot at the right time and wins the playoffs. A case could be made for both. It’s a mess worth avoiding.
As a result, the United States opted for leagues in which teams are set. Once the leagues were codified, farm systems and affiliates were adopted for lower leagues to allow players to be promoted/relegated, rather than the teams themselves. While this does ensure the best athletes are playing at the top, it also does not match the international model for which American soccer aficionados rally. But I posit that MLS *could* have a promotion/relegation system, which we all know will never happen.
I propose a pro/rel system not based on a team’s performance, but a team’s paid attendance. The teams with the highest average attendance per game are showcased in the MLS while teams that fail to draw crowds make their way to lower leagues. This would ensure that MLS teams are the ones that have the largest crowd support based upon a city’s/area’s love of the game, as it should be. It also helps relieve the MLS of having to worry about teams like Chivas, Tampa Bay, and Miami who were forced to scrap their teams due to poor attendance. It’s also funny how a team’s incentive to perform ties directly to a team’s attendance; teams would be more motivated to win if it helps to increase or maintain their overall attendance.
The end result would be a league which showcases the most soccer-crazed cities in the United States, be they major metropolitan areas or smaller markets which love their local professional team. This also allows other teams to begin grassroots campaigns like Sacramento Republic to gain attendance momentum and be rewarded for the effort via promotion while other markets may have plateaued in fan interest are relegated to lower leagues. MLS would have exactly what they want: a presence in the most soccer-loving cities in America year after year.
Of course, the system isn’t perfect. FC Dallas would currently be facing relegation despite being a top MLS team and barely losing the 2016 Supporter’s Shield. Teams like Seattle would never face relegation, either. But these flaws are also found in the European models. Leicester City won the league last year and is in danger of relegation this year. There are usually five or six teams that are never in danger of relegation as they always finish in the top 10 while the rest of the league is scrambling to stay above the relegation line. No system is perfect. But if the United States did want to implement promotion/relegation, paid attendance would be a great place to start.
But then again, who are we kidding? It will never happen.