Have you tried to contact Frontiers? They have a great roster of rock and metal bands. The band that made me ask this is Eclipse. They have made the best melodic hard rock album of 2012 or at least so far (got 100% on MelodicRock.com). Here and here are some samples from the album. It would be great to at least get the title track.
Fly from Here album and Asia with all of their albums since Phoenix. I would love for any of their songs to make it on here.
Moar Grateful Dead:
Led Zeppelin (I can dream, can't I?):
Another band I'd love to see:
I've actually contacted them, and for a long time seemed interested. But this was before the release of Rocksmith. After a while, they turned me down for reasons I don't want to discuss, but maybe if a bigger authoring entity goes after them we can get some of their songs. Their latest album is really good, and I'd love any songs you can get from this band.
Addicted to bad movies since 2008
 Dizzy Mizz Lizzy  Dover  Guano Apes  More Miley Cyrus
 The Rasmus  The Veronicas  More Volbeat
I would also love Work of Art (Enbound has the same singer btw). Their website is quite messy, so here you can see their whole roster. They have so many bands that I would love to get, Hess, Treat, Crashdiet, Pretty Maids and Jorn, just to mention few of them. I'll have to check out the bands that I don't know from that list. The bands that I know are great so I think I'll find a couple of new great bands too.
No idea how Ben Sharp would feel about it, but he's a one man band called Cloudkicker. He's mostly post-metal, but his more recent albums like Loop and Let Yourself Be Huge have diverged from that, too. Specific songs that immediately come to mind would be "Hold On" off of "The Map is Not the Territory", "Amy, I love you." off of "Beacons", and "LA After Rain" off of "Fade". Really though, pretty much any of his songs would be fun to play in Rockband, aside from the really short atmospheric/album flow songs like the opening to "Beacons, "We Are Going to Invert".
Ben's always been really cool with his fans, sharing tabs for his songs and always releasing his music as pay what you want, so maybe this would be something he'd be interested in doing.