Haha I did that too, all the time - until the third game where you could use any spell you wanted at any time and then I'd constantly run around as Hermione using the freezing spell because it looked the coolest XD
My problem with it though is that it wasn't a real spell. It was never referenced anywhere in the books and it was just a convenience spell for the games. It also bugs me because they could have just as easily used Relashio, which Harry used for Flipendo-y purposes in Book 4.
That... I don't even... that sounds like the perfect game. I literally cannot think of a better game than that in the entire world. It'd be like... Skyrim, but in the Potter world. I love that idea so much! I'm just gonna copy and paste your post directly into an email to every gaming company that ever lived. IN FACT! Kura works for a game company, I'm sending this into work with her! We can make this happen, people!
Though unfortunately on a more serious not I think you're right; it never would happen . Particularly if Book of Spells is any indication of the future of Potter gaming.