I went through precisely the same ordeal you stated. However, I was thrilled when i saw Diddy Kong (I love him) in Strikers, which is, by the way, a positively great game.
That being said I would be most dissapointed if the same principle was implemented into Brawl, seeing all the characters without doing all the hard work to unlock them myself.
With Strikers there are only three unlockable characters, thus the same anticipation of unlockables is much less as opposed to Brawl.
I propose they release Brawl and wait for perhaps a month for people to unlock characters and levels themselves and then release the online play. This way everybody would be more familiar with the game and also not spoil the surprises of the new characters.