What if James and Lily had a contingency plan in place if Voldemort made it through the Fidelius Charm somehow (poor trusting babes)? Like what if Peter was killed and someone less loyal spilled the beans? So the whole Potter family gets away from Voldemort that night. Our idea was that they somehow got their hands on a pair of Vanishing Cabinets, so one would be in the cottage and the other would be somewhere safe like Hogwarts, another Potter property, Sirius' house, wherever.
Peter gives the Potters up just as in canon, only this time they all get away safely. Voldemort would try to follow them through the Cabinet but they would destroy the one on the far end and he would be destroyed or trapped in the inbetween place. Maybe Dumbledore or someone eventually destroys the one at the cottage so there's absolutely no chance of him coming out of there.
He would still have all the Horcruxes he made on purpose (not Harry though, so there would be no Parseltongue or visions of Voldemort's mind later one) so he would eventually come back, but the method he uses might be different.
But basically, Harry gets a pretty normal upbringing. There are two ways his life could go: either the Potters go back into wizarding society and are hailed as heroes and all that, and Harry is raised in a famous family rather than being the singularly famous one himself. Or, they could decide to stay hidden for some reason. There are still lots of Death Eaters around, and maybe being betrayed by Peter put them off the public life. That might develop into interesting tension later on if Harry thinks that fighting Voldemort when he returns is the right way to go while his parents maintain caution is the better part of wisdom or some such. That would be hard to pull off considering it's Lily and James, but if their top priority is Harry's (and his siblings', if they have more kids) safety, then that might work.
There are clearly a lot of directions a fic like this could go, lots of which have been explored before in various ways, but we thought that taking out the BWL/being a Horcrux angle would do something really cool to his character, where he'd have to actively go out for the hero role rather than having it foisted on him all his life. And having a healthy home and family life could either set up a character arc like James' where a bratty, spoiled kid turns into a hero and a virtuous person, or just underscore his already positive traits and explain why he wants to save the day so badly when Voldemort comes back.
Pairing: no idea, but we do love Harry/Daphne, as should be clear by now.