If RB doesn't already do this, record yourself doing each of the 6 parts so you sound like a 1-man band with the final result, or you and a friend... at least with the vocal parts. It'd be funky on-screen since it'd be 2-6 different games combined into 1, but it's not my job to fix that.
More songs on disc. Maybe even the entire discography. Actually almost any of the above mentioned things would be great (except Paul being dead ), especially the 3-D Glasses !
Home is where the needle marks
Try to heal my broken heart
Either of these announcements would be mind-blowing:
Being able to play both guitar & vocals with the same character (voxtar), so that you can have a "complete" band with 4 players (instead of requiring 6).
Support for 3 simultaneous guitars (lead, rhythm, bass).
TB:RB, RB3 expert vocalist PSN: Murph_70
Always looking to friend other expert players!
Exportability or venue change. Neither of which will happen.
Or story mode DLC, which is entirely possible.
"The man who keeps running, never looking back, because he dare not, out of shame."