I know it's never going to happen, but I'd like to see the league get up 32 teams and then split into MLS1 and MLS2 (16 teams each league). Teams would move between the two leagues through promotion/relegation but the teams in both leagues would still share the same revenues so there's no financial disadvantage.

In both leagues:

Schedule: 30 game, balanced scheduled.
Regular Season: #1 seed gets supporters shield in MLS1, #1 seed in MLS2 advances to MLS1 playoffs.
Playoffs: Top 7 seeded MLS1 teams make the playoffs, #1 seed from MLS2 makes playoffs. Single elimination until there's MLS cup winner.
Pro/Rel: Bottom 4 teams go down, top 4 teams go up