Just to elaborate further, being horrendously cold to Tifa only changes the Cloud-Tifa Highwind scene near the end of the game, while it can have a potential effect on the Gold Saucer date.

Anyway, aside from the fact that Aerith and Tifa's roles being reversed would change the second half of the entire game, if it were possible, a GameShark or game code-hacking device would have found it by now.