Yeah, but there's another solution.
How far you've gotten in the single player game lets you access the console commands and multiplayer features.
Color and SKIN commands are unlocked from the start.
Beat Greenflower Zone, and you get Talk button enabled, as well as being able to join netgames.
Beat Techno Hill Zone, and you get the ability to add files to the game and host Co-op netgames.
Beat Castle Eggman Zone and you get the ability to host Race netgames and get the Changeteam command.
And so on, until you get all the commands. Beating Special Stages unlocks nothing at first, but eventually lets you do STARTLIVES and STARTRINGS in multiplayer, at the sixth and seventh stages respectively. Beat them all twice and you get the GRAVITY command.
All of this can only be unlocked in single player, so it forces people to do stuff there before they can do anything in Multiplayer.
How far you've gotten in the single player game lets you access the console commands and multiplayer features.
Color and SKIN commands are unlocked from the start.
Beat Greenflower Zone, and you get Talk button enabled, as well as being able to join netgames.
Beat Techno Hill Zone, and you get the ability to add files to the game and host Co-op netgames.
Beat Castle Eggman Zone and you get the ability to host Race netgames and get the Changeteam command.
And so on, until you get all the commands. Beating Special Stages unlocks nothing at first, but eventually lets you do STARTLIVES and STARTRINGS in multiplayer, at the sixth and seventh stages respectively. Beat them all twice and you get the GRAVITY command.
All of this can only be unlocked in single player, so it forces people to do stuff there before they can do anything in Multiplayer.