I've always had an idea for a set rotation thing, and I think being the given format of this tour set list it would perfect for it.
About 3 months before tour, get a rough set list together, and have about 30 songs prepared. If you're average set list is like 18 songs, pick 10 songs that you know you're going to play and extract them. Then leave the other 20 possible songs out and do some kind of online voting where the fans attending each show can go online and vote for what they want in the show they see. I tink it would make for really excellent shows.