Agree and disagree
I agree 100% with the turn-by-turn direction map concept. Then again, why should Apple still use Google Maps when there are so many better programs. Google is getting too powerful for Apple to rely on. It is a great search engine, but, like Apple, it takes it's popularity for granted. And somehow, Google receives some strange sort of respect for it's mediocre, mostly 2-dimensional, low-detail map.
I also do not think that the multitasker needs too much improvement. The way it is expressed by you makes me think you want it to be a full-screen feature. That really eats away at the idea of convenience. Your request for more wallpapers is also pretty useless. If people want more wallpapers they get an app and erase it later or find a website that has some good ones.
New Siri functions would be nice, but there would probably not be too many third-party apps you could interact with past entering them with Siri. If your idea of Facebook integration becomes a reallity, possible you could post to your wall, or Tweet with Twitter. A hint to this is that the current Siri was programmed with the knowledge to admit that she could not send Tweets currently.
You complained about the lack of location-based weather, though there already is one. You just enable it in Loaction Services and you get a Local Weather location in your Weather app
Deleting Apple's built-in apps is a little rardical. You should just be able to go into Settings and "turn them off" your personal data in the app would be saved, but the app would not appear unless you turn it back on in Settings. Of course that means you cannot hide the Settings app.
I do not think you mentioned it, but I am glad you did not mention widgets. Some may find them usefull, but I just see them as a waste of space and a lack of order. It is one of the things that makes Apple's so called "boring OS" so distinguished though many hardly know it. Putting them in the Notification Center for non thrid-party apps only might not be to bad, but for apps outside of integration would be a little risky for Apple's perfection.