For me it would depend entirely on what the project is aiming for. Due to my own interests the top pick would be playing as an intelligent "monster" in a consensual relationship, but that would only be worth it with a proper payoff in consensual monster+tentacle sex, cumflation, egg-laying, the works.
For a story-driven game being some kind of newcomer is crucial. Could still be anything from a muggle roommate to a trainee teacher to a freshly turned vampire or werewolf in an "animal shelter" but basically if my character is supposed to be a trained wizard (let alone a wizarding headmaster, the demon overlord of a witches' coven or something similarly impressive) I expect the game to let me USE that power as I see fit. And I have zero confidence a lone dev asking for advice on a porn forum can do that justice when even large mainstream studios struggle to balance PC power and story integrity. On the flip side for a plotless sandbox like Stationmaster the more power the better.
The other big question I immediately have is what role the magic will play in the story. Just a colourful backdrop for mundane "slice of life" content, as it was for many social situations in the earlier Harry Potter books? A handwaving excuse for game mechanics (weird economics? mind control? transmuting clothes?) or sexual fetishes (exhibitionism with an invisibility spell? hentai-grade aphrodisiacs? tentacles?) - related to that question, you haven't given any information on the wider setting either. A "school of witchcraft" could be anything from Hogwarts to the "Japanese highschool occult club" to a high fantasy world where half the people are elves or orcs.
Basically with how little information you've given I can't provide any meaningful input beyond listing sexual fetishes I personally like, and I know those won't appeal to many other people.
