FFVII is the most known title in the franchise worldwide and it's far recognisable enough to need any more reference than what they already have (*cough, cough* the VIIth legion trying to bring down a meteor on Eorzea, the Weapons, the magitek enemies inspired from FFVII mob, Unknown from Anamnesis).

If they're going to bring stuff from other Square Enix titles, I would rather they brought stuff from the less internationally known of titles, like they pretty much did with FF3, FFT and Tactics Ogre.