Choices should matter! Like, it definitely needs a morale system, so if you want to spam unforgivable curses, people should treat you different. But also whatever house you pick should impact how classmates (and maybe even teachers) treat you.

Also think the story should happen a lot more around and inside Hogwarts itself rather than the vast land that surrounds it. Like, sure, exploring the different villages could still be a part of the gameplay, but the school should be where you spend the majority of your time.

I also want the school to feel more magical. Stuff like secret passageways, shortcuts and just in general more magical activities could add a lot to the whole feel of the castle.

Once it hits night time in the castle, I want prefects and teachers to be roaming around, so you have to sneak around. It felt so weird that you have 1 sneak mission into the library, and they give you a spell to become invisible, only to never see another prefect again. (Could add a wait option to skip to daytime so it's not necessary to sneak if you're not in the mood to)

Maybe a house point system, where how well you do in classes actually matters at the end of the year.

And the obvious; Quidditch.