JK wrote the ending well before she had completed the last few books and kept it securely locked away. It shows - it's neither very well-written, nor does it make complete sense, so I usually skip it.
Ron/ Hermione should have been a romance born out of shared trauma, but later on Hermione would have been dissatisfied with having to provide Ron's creature comforts while Ron would still have lived in someone else's shadow. Once the trauma had worn off a bit, both would have realised they're not made for each other and split up among their many arguments. Ron would then have gone off with a Hufflepuff while Hermione would have ended up with a Ravenclaw. She was a bit like McGonagall in that the sorting hat was choosing hard between Ravenclaw and Gryffindor anyway.
Harry and Ginny - I can see that working well, but only with the book characters.
Hogwarts professors are all single like old-style teachers were expected to be. Dumbledore never loved again after Grindelwald. McGonagall lost her husband early on in life. None of the DADA teachers were in relationships and the others were either too old or too weird to really pull. So Neville would likely have ended up single, too - a shame, as he bacame quite a catch from HBP onwards.
Luna would eventually have found someone into research like her, but with a more grounded side to him. The complete outsider from the story might work well.
Interesting that someone mentioned Hermione's parents. As far as I am aware, damage done by magic can never be reversed - it's why Lockheart was confined to St Mungo's forever. So how could she have reversed the spell?
I think Molly ended up even more paranoid about her children after the death of Fred, so she would have been an overbearing nightmare of a MIL.
Draco was disgraced by the time DH ended. He shoud have become a loner and probably quite bitter as his riches and comforts entirely depended on his parents' money. Quite possibly he woukd have ended up a drunk - I always imagined Lucius to go that way, too.
Snape... he was consumed by bitterness. I know Alan Rickman made him into a kind of weird sex symbol, but no - even Rowling said that she never intended for him to go that way; his bitterness just made him a cruel person. Yes, he was tragically in love, but he was also almost stalking Lily throughout their childhood and had no issues allowing James and Harry to be killed for his own greed and desires. He didn't reform, he hated Harry because he hated James and the only thing he cared about were Harry's eyes to allow his obsession with Lily to carry on and fuel his bitterness. A bit of a masochitic move, really - maybe punishment for what he had done. Killing him off was the kindest thing she could have done for him; he would never have been happy with any other woman and if he and Hermione had ever got off together he'd have turned into his wife-abusing father.
Sorry, I am very over-invested. To the point I refuse to read CC - I've only read the bit with the trolley lady and it was enough to put me off the entire play.