Aeris was supposed to live.

[Rengori]

By this logic, there is no reason to stop Sephiroth since Aeris's pray for Holy would have worked. Aside from changing
a lot of Diolaouge, it would change the entire story, as well as several cut scenes. And, going by this, you obviously don't Squall very well do you?

Well actually it proubably wouldn't have changed it that much, I mean, all they'd have to do is write in another reason for Aeris's prayer being interupted. Aside from that, Aeris living really woudln't have made much of a difference.

Let's see, Aeris would have gotten Holy to work without Sephy dead, Meteor would not have been summoned, there would be no reason to go to the north crater, and the WEAPONs wouldn't have unleashed hell on FFVII's world. Little story change?