Honestly, Tifa being a bottom makes sense even in the original; the whole point of the characters and their designs in the first game was subverting their appearances. So while Tifa's a tough martial artist, she actually embodies a lot of the Yamato Nadeshiko tropes. And Aerith looking like a pure maiden flower girl, but she'll tease and flirt and use her wiles on guys. Oh, and remember that it was Aerith's idea (and is in the remake too) for Cloud to crossdress.