Now, there are about 30 good reasons why Rock Band proper shouldn't have boss battles. But Blitz? Blitz is a game with giant pinballs and rocket launchers. You could totally fight a boss using giant pinballs and rocket launchers. It's also easy to picture a boss having attacks that you have to dodge by avoiding a certain track, or projectiles that you have to reflect back by moving into a certain track at the right time, and depending on the other powerups that haven't been shown yet there may be other clever elements that could be exploited to have a sense of combat without sacrificing the overall goal of hitting as many music notes as possible over the course of the song.