It's more likely than you think.
99, lead character of my comic Felicity, totally playable in Rockband thanks to the create-a-rocker. I've had to put her in 'Civis', going mainly with her 'Volume 325' outfit.
I also totally have the greatest guitar ever. No, your eyes don't decieve you, that really is a Pikachu guitar. I'm just that AWESOME*
It really is awesome though, rockin' out as my own character.
I never bought Rockband because I didn't see the point when I heard Guitar Hero:World Tour would feature the same variation in instruments. Eventually though, the wait and the temptation finally succeeded and I caved in.
I don't regret it, I think it's actually miles better than GH, the style is ace and it's just so much fun to play. Which is something so few games seem to succeed in doing these days. To actually create fun.
*Sad, very very sad individual.