I hope for Lessons and Practice Drills - I think it would be great if there were lessons.
1. Chord Changes on rhythm.
2. 12 Bar Blues.
3. Strumming Drills.
5. Chord Shapes. Guitar is a shapes based instrument, but I didn't learn that much in Rocksmith.
I would want each of these, of course, to work the opposite of Guitarcade games, by having me play in rhythm, on time, with tunes that make sense or are in key - and when doing the chord change game, I would want a proper Chord Box to show up. If you already know all the chords, the games are fun - if not, you just sit there not knowing what fingers to use where or what shape to make.
Essentially, my ADHD stops me from learning from videos/online classes. If there were something like a Justin Guitar DLC, that would be great.