I was watching videos of John Paul Jones playing mandolin with the Dave Rawlings Machine and Robert singing with Patti Griffin and thought, "Okay, so Robert can't sing loud and hard like he did in 1970. But how about an acoustic reunion? I would be there!" The Earl's Court acoustic set was the best part of the DVD, in my opinion.
The only pitfall I can imagine is the audience being rowdy and restless. They would have to play arenas and acoustic music doesn't travel so well in there. But whatever, it would be a compromise that could work for everyone.