*brushes off soapbox and steps on*
I apologize ahead of time, but...
Well one of my BIGGEST issues with Harry Potter fanfiction, especially since Book 6, has been the habit of the fanfiction community to essentially slander and crucify J.K. Rowling for writing HER series the way she sees fit. If you don't like it fine. But don't say she ruined the characters or anything like that. She created them, and, to hear her talk, she had a plan for where they'd end up all along.
*steps down*
Now that that's out of the way, as much as I enjoy the various fan-versions of Snape, I do believe that Snape, as he was portrayed in the books, was all to real. People like that, much as most people don't like to believe it, do exist. Normally they'll do something stupid and get slapped with a restraining order and/or prison time, but then again, Snape only got out of it because Dumbledore had a use for him.
So, while I would LOVE to see this story worked out with a fanon!Snape, I think it would be an even greater challenge if the author were to work with canon!Snape as a deterrent and have some Slytherin's decide that they're tired of the bum rap they've been given simply because a thousand year old enchanted pile of rags stuck them with a label and work to redeem that label in spite of Snape.
Edit:
Dhampyr, while Azkaban may be the Wizarding prison of note, the presence of Dementors makes it, in my opinion, cruel and unusual punishment no matter who you are. Thus, while Sirius did deserve jail time, he didn't deserve Azkaban.
Nobody deserves Azkaban.