This is a personal view. This is based on personal experience and on personal feelings and believes to create a great game, a great RPG. There is plenty to not agree about and you might be right. It is merely my personal view on the matter. It all started a few hours ago when several Hogwarts legacy videos passed by, I looked at one of them, and soon thereafter turned it off. For the most so that I will not be hit by optional spoilers. I also saw a few headlines on how it might be bad, how some people claim to be experts. I am not one of them, I merely give my view and it is not connected to any part of the Hogwarts or the Hogwarts storyline.
Part 1
In part one we need to set the ground rules. As an RPG, I believe that the largest power is replayability. So when we use the HP movies as a backdrop the game will need 20 main story lines. 4 houses, each house has its storyline, with 4 intersecting stories. As such if you start as Hufflepuff, you get the Hufflepuff story and the three non-house stories and one generic story. That makes 20, also each house will have 25 side quests (could be 50). As such we end up with 100-200 side quests in total. Finally there is a red wire and I personally think that JK Rowlings should do that. 4 small books of 50 pages each, every storyline will have 50 hidden pages, it is about (for example) the origins of the house makers, Godric Gryffindor, Helga Hufflepuff, Rowena Ravenclaw, and Salazar Slytherin. The story is only revealed when all 50 pages are found and then a small booklet will unlock on the system that the gamer can readSo after 4 play throughs all 4 books are available to the player.
In that setting when one game is completed a new Game+ is selected and you go from the beginning, yet in the second game any of the three minus the one you already played becomes available. Now we have a game people will run to the shop for.
Part 2
All what I write would still be possible in the game no matter how it is staged, not even the storyline is messed with, that can still be there. As such the four generic stories will be connected to the house, but will not be connected to it. As for the side quests no more than 10% can be replicated to other houses, so it will be a large stage. It also comes with limitations (I love those). Side quests on potions are only available to Slytherin players (as the potions master was Slytherin), Gryffindor and Ravenclaw will get magical creatures quests and so on.

As the screen shows, each house has quests that link to a non house, so if you had Gryffindor in game one and Ravenclaw in game two, the second game will offer a rerun of the Magical Creatures side quest, but none of the others.
I believe that in such a way a massive wave of replayability is offered whilst at the same time offering a large fountain of playability. It would create a direct dent in what Bethesda offered in its games, it would be close to unparalleled. And let’s not forget the number one rule, it is merely my take on the matter.
It is merely a small part, and this took me less than an hour to think through, more? Yes, naturally, please ask the makers of Hogwarts Legacy and if they want to use what I just wrote, it is for them and to at their discretion to use, a simple equation.
And I leave you with the small stage. This took an hour (at the most), so why can’t Ubisoft come up with this stuff? They are the multi billion dollar corporation, so what is taking them so long?