Considering that the Chorus Kids have no correlation with Mewtwo, K. Rool, or Ridley, they shouldn't be blamed for any of their exclusion, and it's asinine to think otherwise.
Rhythm Heaven is a pretty big series and it's HUGE in Japan. Representing a new IP is just as important, arguably more so, that representing an already represented IP. Now my opinion may not be appreciated here, on the Ridley thread, but I'm a big fan of both the Chorus Kids and Ridley, and I find it aggravating that Chorus Kids would be blamed for the exclusion of Ridley.
Heck, I can blame Little Mac and Mega Man for Ridley's exclusion.
Same difference. And I freaking love them too.
It's alright not to like Chorus Kids, but they have no effect on your favorite character, whoever it may be.
Ridley will get in on his own merits.
PS: Mewtwo will be in this game.