Not in any particular order but here are my ten most wanted. Most of which could be done via update in RB1:
1. Band World Tour Online - duh. No explanation needed.
2. DLC backwards compatible - simple, make sure the small fortune I'm spending on DLC works in future games.
3. Supergroups in Solo Tour - I have a drummer, a guitarist and a singer, why is only one used during Solo Tour and I get paired up with generic NPCs? If I'm on my guitar tour, toss in my drummer and vocalist to back me up instead of fake NPCs.
4. Gold Stars - they are damn addicting in GH, it is quite lame it is relegated to Expert only players in Rock Band. Bring 'em back to all the other difficulties as well. Give the less than phenoms something to shoot for.
5. Custom Setlists in Solo Tour - Ability to make a 2-10+ song set so I don't have to go back to the song list after every song I play to find what I want to play next. (GH needs this as well)
6. Better setlist organization - Having DLC at the bottom of a 60 song list is terrible design. Take a page from GHIII, make tabs for In Game, Bonus, and DLC for easy navigation. The DLC page needs to be sortable as well.
7. Bass Solo Tour - Why not? It may not be the most exciting 'Tour' but it would be something different. All the elements are there, I don't understand why this wasn't in the retail release.
8. Join Multiple Bands - I want the ability to keep my character(s) on a memory card and temporarily 'join' a friend's band for his World Tour instead of creating/storing a seperate character on his system.
9. Disallow tracks - the ability to check off certain songs you don't want showing up in random setlists. Keep the main game setlist off-limits, but allow me to check certain songs I've bought as DLC that I don't want thrown at me at random.
10. HO/PO Notes - These notes need to be more distinguishable. The tiny notes don't cut it. They need a glow or something.
bonus:
11. Camera support - other games do it, so why not become the total nerd rock star? Map my face to the character I create. Allow me to snap a photo for my band logo instead of some generic paint tools.
I'm not even going to touch hardware revisions. Other than the mic everything else is a cheap P.O.S. Once they get those right, then we can talk about tweaking them.