Yes, it would be interesting...but you cannot see the evil win twist never in stories like these, for stories like these cary a message about hope for better tomorrow. Moral values are presented here, lessons to be learned....unfortunatelly as it was pointed out previously, FF7 follows a very old pattern. All these games follow the same twist..same story retold, same characters renamed...SE with their FF series is an expert in repeating the same old story and selling it to us all under the new package.
Hero/Cloud vs the ultimate representation of evil/Sephiroth. It does not matter, pick any character of FF, it is always the same pattern, it does not matter if the hero is Cloud, Tidus, Sora, Squall,.....it is a stereotype... always, and they go through the same ordeal...the evil side too, same character each time. It can be applied to many other games too...I am not picking on FF here

...and we play them and we love them for what they are...
But the point is that evil under any circumstances must be defeated.
On simple terms the final battle..you bloody must win, cos then the game has no point...you gotta beat him to beat the game...itsn't that obvious
You defeat the evil with your party, and love and friendship wins there on one hand as the party fights for the world, but on the other it is Clouds fight, it personal for him...that is why you get that final blow only with Cloud, and that why Sephiroth cannot hit back. This is Clouds game first of all.