Well so I decided to post a challenge as I got this plot bunny right now but I myself don't have time for another project with two already and school +GCSE so it comes
In this if someone to ask for epilogue it's just going to be 15/16 years later instead of 19 but it's really up to you.
Harry and Ginny didn't get married however Ginny got pregnant with James Sirius just after her graduation.
Harry just finished his auror training and is tested for any potions ever used on his as it is discovered that he was force fed love potions and after further investigation it happens to be Ginny and thus he decides to leave her and took his son away as Ginny didn't have enough money for his keep and also told her to move out of Potter manor.
Prophet got a news of it and publish that Lord Potter-Black is now alone father which becomes scandal.
With such news Lord Greengrass decided to send him letter with pretense as to why he ignored his daugher and marriage contract that he signed with James Potter with witness of Charlus Potter (who died just week after the contract was set following only three years after his wife) and knocked up some girl that were never to be with him.
And that as the contract said Harry must marry Daphne Greengrass within two weeks before his 20th birthday or Daphne and Harry die.
It becomes known of the fact that Dumbledore hided some information and killed the goblin with knowledge of such as to not cause Harry to come to light with the manipulation he's doing.
And now Harry has to marry a girl before known as ice princess and a Slytherin that many will run away from.
May be done before but I don't think so and well hope some people will write this story.
As for other pairings I don't really mind and it's your choice however it is preferable is Draco/Astoria.