Post-DH, EWE: a twist: most of the Wizarding world, including Harry's friends, had a change of heart about Professor/Headmaster Snape after the truth came out about his great sacrifices and contributions to the war effort. Snape is considered a great hero and is lauded by the masses. Only Harry still stubbornly holds onto his hate and refuses to forgive him. Snape on the other hand loves Harry and tries constantly and in all kinds of ways to win his approval, forgiveness, love... Harry is annoyed that all his friends not only think he should be with Snape, but they all try different schemes to get them together. :-)
Romance: Third person POV fic (or could also be called "bystander!fic"). In other words, either the whole fic or considerable part of it is told from the point of view of a character who is neither Snape nor Harry.
Snape's family: An alternate explanation for the scenes in Snape's memory that are always interpreted as him being neglected as a child and Tobias being abusive to Severus and Elaine. Here are a couple of suggestions: 1. Harry travels back in time and somehow causes the fight that he later witness (accidentally or not) as a memory in Snape's mind. It would be good if, at the time when Harry was seeing the memory, Snape actually knew it was Harry who "caused the fight". Maybe Harry had an affair with Snape's mom? So both of them can claim to have had something going on with the other's mother? lol 2. Maybe Tobias was angry at Elaine for letting little Severus go visit his mother's family (the Princes) who teach him all sorts of nasty dark magic and fill his head with blood purity nonsense.