I'd like for them to have 8 to 10 extra songs down pat, and mix up the set list just a little bit each night. Each crowd gets to walk away knowing they saw a unique, one-time set. I love seeing bands (e.g. Wilco) that do this. But I respect that FMac are getting older and older, and it is a blessing they're all healthy enough to tour at all (knock wood that'd still be the case next year)
I'd like to see more songs that feature a combo of Lindsey/Christine/Stevie, and fewer that are like a 4 minute "solo act" (e.g., really don't need to see Stand Back again on a Fleetwood Mac set list... ditto for Acoustic Big Love). Choices here could be things like Honey Hi (from Tusk), Crystal, World Turning, and their gorgeous cover of Farmer's Daughter (Beach Boys)...