I may be able to give some insight on this.
A few years ago, I was part of a small RP tabletop group. A guy named Tom was our game master and he whipped up a Harry Potter RP with dice. It was the most brilliant thing in the world and I'd love for someone to possibly incorporate the experience through here.
We had a character in the group who was 3 parts human, 1 part dragon. Gold things made her neeeeeeeed them. Any time she saw something gold, she had to have it. She was the best friend of my character. A mutual friend of ours had the last name of LeStrange. Oddly enough, he was placed in Gryffindor. I'd advise that there be a signup sheet if you go through with this. Go as far as to do research on those who want to play complex characters (for instance, a character who is part dragon). Make sure they can play those characters. It's something that can make or break the RP.
The story was very deep and very rich. We were placed in the "future" so to speak. After the Harry Potter story had already ended. There were other professors in our game as well. In this time frame, magic became a thing that muggles were vaguely aware of. It was feared by some, embraced by some. However, magic was the cause of the fall of Big Ben (the huge clock tower in London). Because of this, witches and wizards became victims of hate crimes among the muggle world, which my character fell victim to as well. This added great conflict.
If you decided to go through with this RP, I'll happily help and play. :)