Draco breaks a time turner and starts jumping around in time (very similar to the premise of the Time Traveler's Wife). At first when he sees he's married to Hermione in the future, he's horrified and fights against it any way he can. But the love he sees in the future is unlike anything he'd ever imagined for himself. Meanwhile, his future self is coming to the past to charm Hermione. When they both meet up in the same time, things get fun. Romance / Angst / Drama. Post-war, not epilogue compliant, happy ending (that the characters have to work very hard for).