I would have really liked to see mini-movies of what happened between the seasons, especially between:
S2 and S3: Joyce storming into the library and demanding an explanation, Giles trying to explain and Joyce freaking out on them, Xander and Willow being there for her through her break downs and guilt-trips - which will explain Xander's "You didn't see what she went through." Giles suffering nightmares of torture, Jenny's death, Buffy leaving on a nightly bases. Xander and Willow asking Giles for a plan to slay the vampires since Buffy isn't here, Giles being too busy looking for Buffy to care, Xander, Willow and Oz taking it upon themselves to protect Sunnydale, which was difficult at first because Willow was still weak from her injury and Xander's arm is still in a cast.
S5 and S6: Xander taking Anya to the hospital, the quiet Buffy funeral, Willow and Tara moving in with Dawn, Xander and Anya telling Xander's parents that they were getting married; Xander snapping at Anya when she was about to reveal that her family were demons, right before Xander's father snaps at his mother because she forgot a beer bottle or something which triggers Xander's fears about the possibility of turning into his father. How the Scoobies decided to use the BuffyBot? Spike fighting side by side with them.
S6 and S7: Giles taking Willow to the airport, only Xander was there to say goodbye. The formation of the Buffy/Xander/Dawn family unit. Tara's funeral - Buffy and Xander taking care of everything. Anya ruining people's lives unhappily.