The issue is that the very creation of the Big Materia would drain the planet of its life force, so I feel the damage is already pretty much done, unless there is a means to reduce materia back to pure mako energy the plot never tells. While materia does occur naturally, it's also stated to be incredibly rare to occur, whereas Shin-Ra is mass producing it. Granted, using materia also drains the life out of the planet, but that was something stated in interviews discussing why Cloud and Co. don't use materia in Advent Children, so it's unknown if this information was something the developers knew when they originally wrote the game, or something they conjured up for the remakes.

Honestly, I feel the quest would be an easy fix if they simply changed around a few parts of the scenario. All they need to do is have the party consult Bugenhagen about the Holy Materia before the quest really gets underway, and maybe have him add a line about how Shin-Ra's plot is pointless and won't work. Would largely fix one of the most glaring plot holes in VII, besides the existence of the Black Materia, or how Sephiroth's plan is kind of counter-intuitive in places.

Speaking of glaring plot problems, I hope they fix the logic of Cid's recruitment as well. It just never made sense that Rufus traveled all the way to Rocket Town just to commandeer Cid's plane. It's established he already has an entire air force, those helicopters would be much superior for tracking down someone, and why is the head CEO bothering with grunt work? The whole scenario is pure silly RPG logic.

As for the battle system, it's unknown at the moment how it actually works. The rumors I posted suggests it works on the same logic as the ATB gauge from FFXIII, where the characters can perform multiple actions with each action costing a piece of the ATB bar. Once you're out of ATB gauge, you have to wait for it it to refill. Depending on whether the game gives it a more action game feel with dodge rolls and blocking like Crisis Core, the game may end up playing a bit more like a flashier Dark Souls.