Well, that seems generally reasonable, although I'm not sure how someone like Arc would fit in here, since she's not a student and she's not from Misaki originally.
The Sakura thing also seems fine, but it does raise quite a few questions. For one thing, when was she saved (which affects whether Shinji was ever a dick)? Secondly, what happens to her afterwards? She could go back and live with Rin, potentially, but that would have to be set up. Otherwise, I'm not sure. Remaining with the Matous after being saved would be odd, although if Shinji never started abusing her it's possible. Ciel could also take her in, but she doesn't really seem like the type to take on a maternal role.
Also, what about Shirou? What sort of relationship would she have with him? Also, how would Kiritsugu remaining around affect his development?