BUFFY THE VAMPIRE SLAYER and all the characters in this story (even the unnamed newspaper seller) belong to Josh and Mutant Enemy.
This story was inspired by the story THE MIRROR NEVER LIES by Lafe which you will find elsewhere on TWISTING THE HELLMOUTH. It in turn was inspired by someone's challenge. But while the basic idea, that the season Seven Scoobies met their Season One counterparts, was very appealing to me, the idea (included in the challenge) that the future Scoobies would hang around and fight alongside their counterparts was not so much fun. So this, though inspired by other fanfic, is not an answer to a challenge.
There's no fighting here, much angst and a whole bundle of what is I believe called 'fanwanking' where I speculate to fill in some of the background of canonical bits where I thought they needed expanding.
The idea of Buffy being given a Wish by the Powers as a reward at the end of season 7 was floated around for a while as an alternate ending that got left on the cutting room floor: I don't know with what provenance. I just stole it and ran with it.