Well, if summoning Rider is allowed, then Sakura wins. Otherwise, yeah, I think it's difficult to see how Sakura could beat her, but I think the general point of the thread was not to work out who would win, but to see if we could find a way that the underdog in the fight could actually pull off a shock victory. After all, no fight is a certainty.
Also, I think you're over-exaggerating the amount of effect that AM has on Sakura's magical ability, at least in the long term. I think that, with training, normal Sakura is capable of using most if not all of the magic that she uses in her dark form. The only major limit is her prana supply, which is lessened somewhat. And, as for Ciel's immortality, Sakura is one of the relatively few people for whom that is not actually a massive problem, because she is capable of swallowing people and imprisoning them in her shadow dimension, which doesn't kill Ciel and, thus, would not be affected by her immortality.