Fanfiction Writer: Overwatch lore sucks! It has no romance! Clearly EVERY STORY needs romance to be in any way good! If Michael Chu won’t write that into the story I WILL! It will DEFINITELY be EXTREMELY WELL-WRITTEN and NOT AT ALL CRINGEY!" /s
Moircy = Moira + Mercy
“Dragged into a militant organization against her beliefs, Mercy toiled away day and night trying to make the world a better place. But as the endless wars of Overwatch dragged on…so did her faith lower. It was then that she met…that special someone…Moira, Mercy’s opposite! Moira had a vision of a world ruled by pure science. Her hypnotic charisma touched something in the cold and dispassionate Mercy’s heart that she had never felt before. And so, with a heavy conscience, Mercy would begin her dark, twisted affair with Moira…a woman she both loved and hated…”
Gency= Genji + Mercy
“It was during Overwatch’s endless ‘peace-keeping’ that Mercy found him. A man near death, clinging to life. Mercy managed to save his life, but the man was bitter, and he cursed a world that had robbed him of his life and body. And so he left vowing vengeance with anger in his soul. Cynical and embittered, Mercy never became close to another patient. But one day, that man returned. Genji had found peace at last, and came to thank the woman who had saved his life. Mercy felt hope for the first time in many years. So began the story of Mercy and Genji…”
Pharmercy = Pharah + Mercy
“Disillusioned by the failure of Overwatch, Mercy lay low, traveling only to places where she could be Angela. But one day, she saw her, Pharah, the friend of her youth. Despite also witnessing the destruction of the place she held dear, Pharah still truly believed in Overwatch. Touched, Mercy went with Pharah. Together, they would go on many adventures…and it eventually turned into something more…”
Reaper76 = Reaper + Soldier 76
“As life-long friends and comrades, Jack Morrison was devastated by the betrayal of Gabriel Reyes that destroyed Overwatch, and he swore to spend the rest of his life righting the wrongs of Talon. Vengeful, Reaper swore to destroy the remnants of the organization that he had once built. Although he knew it to be impossible, Soldier 76 never gave up hope that Reaper would one day come home. Perhaps then, they would resume their relationship…”
McHanzo = Mccree + Hanzo
“Hanzo sat in a lonely bar. There was only one other person there, a dapper gentleman eating a slice of pie. The man asked Hanzo what he wanted, but Hanzo refused to talk to him. Several drinks later, Hanzo finally expressed his long-held secret. ‘WITH EVERY DEATH COMES HONOR. WITH HONOR, REDEMPTION.’ The man removed his hat and said the words Hanzo would never forget. ‘THAT’LL LEARN YEH’ and ‘THIS LIFE’S NEVER UNEVENTFUL.’ Touched, Hanzo yearned to see where this free-spirited stallion would take him…”
Fanfiction Writer: “There! Excellently written! Clearly masterful work worthy to be put into the canon of the OW universe!” /s
Edit: Forgot about WidowTracer
“Tracer truly hated that blue assassin who had killed Mondatta, someone Tracer had truly respected. She couldn’t think about anyone she hated more. But one day, she discovered a TERRIBLE SECRET! Her beloved Emily WAS ACTUALLY WIDOWMAKER! Widowmaker had disguised herself by changing her name to English and ‘befriended’ Tracer only to manipulate the Overwatch agent. Tracer was torn…but she knew something had to be done, and secretly Widowmaker had developed a desire that surprised even her…a love for the British…”
( TL;DR Yeah idk. I just figured since most ships aren’t well-defined or even present, might as well write what I imagine people think they look like. Was an…interesting exercise. Let me know if it causes your eyes to bleed. 
)