Well, Rock Band did have little "track packs" that seemed to only be sold in Wal-Mart, Best-Buy, and Gamestop, and some of them were "Metal" or "COuntry" or "80's".
I think the best idea would be to release a Rock Band 3, give it a password like the past so all the 1 and 2 songs will transfer to the hard drive, and can be played, then just add a lot more customization, and keep doing the song downloads, and of course add about 100 more songs, then leave it at that, and release all the songs possible they can think of. That would be a good idea. Go ahead and have Jimmi Hendrix DLC songs and full albums, I don't want a game centered around him, not at all.
As for the "lighter" controller and such, did any of you see the Guitar Hero episode of South park? That's what it reminds me of, where Stan had to resort to "Heroine Hero" to relieve the stresses of scoring over a million points in concert. If you haven't seen that epsiode, I highly suggest you look it up and watch it.
How about a "Godsmack Rock Band" where they put the microphone on the drumset and force you to be just as talented as the lead singer of that band and make you play the drums and sing at the same time.
How are they going to have a singer for Hendrix, if he was the singer? You have to play, and sing at the same time? What about the songs he made when he didn't sing? You have to have someone sit near the microphone and wait for time to catch up with itself? Do you have to go to a friend's house, take their guitar, and light it on fire for star power? It just doesn't make sense. It's like having a Jethro Tull Rock band, or Britney Spears Rock band. I don't want it and I don't want to play it.