Xander didn't join the Air Force directly, but he did join the reserves. He remained a civilian contractor and helped the Air Force learn the secrets of the repository. He continued to invent and patent his inventions.
Cordelia and her father moved Chase Holdings and she and Xander had a long and happy life together that included children. Kari grew up, married and made a life for herself as well. Faith visited them often.
Willow and Tara loved each other as well and also had a long life together, settling in Cleveland near Buffy and helping her keep the city safe.
Giles rebuilt the Watchers Council and made it as it was meant to be, a support for the Slayers, modernizing it in the process.
Joyce went from Scooby Mom to Scooby Grandma quite happily.
A/N Robert, I hope I've done your idea the justice it deserved. I am so glad I decided to start posting my stories, the response has been wonderful and 99% positive.
If anyone else has an idea they'd like me to consider expanding into a story, please pm me. I'm ready to start a new story.