I would like to see a (real)guitar-centric music game (like Rocksmith) that allows people to input their own songs/guitar tabs. I've always found the limitations that licensing entails very off-putting.

Edit: just to clarify, I meant being able to look up whatever song you want, and then importing the tabs into the software so that you could play the song using the visual format that Rocksmith has (falling notes fretboard style).