Cotains some heavy spoilers:
The idea about the whispers is not that easy. The whispers altered already the time line and they were actually responsible for the changes happend in FF7R.
- they have intervened Aerith before the actual stroy begins and before cloud meets her.
- they actual saved biggs and jessie (jessies gloves are also on the dresser) and of course wedge (to a certain point at least, chance is very high he survived also the HQ stuff). This isn't the result of the final chapter since they have to be rescued prior to this state.
- since sephiroth has seemingly direct control about the whispers, it seems the whispers were just an another kind of control to keep the meteor hitting the planet. The planet is already tainted by jenova cells (her head is fallen in the stream). Why not influencing the whispers this way?
- Maybe Red XIII has misinterpreted what he has seen. Maybe it's the locked up and now freed origin time line.
- Stamp is still a dog with a military helmet. Could taken as a hint that some changes may happen, but the core itself stays the same.
We also shouldn't forget that the remake needs much, much more fodder in order to convey a believable story. The first chapter of FF7R alone would have to have more text than the whole FF7-original.
In its form FF7 was perfect at that time, but the story at that time couldn't have been told again, because there were simply too many unwritten plot holes and actually too little motivation for most of the characters to make a contemporary Oscar-worthy project out of it.
In my opinion the developers solved the problem of fan service, fidelity to the original and new narrative style quite well. A player who doesn't know the original will also take the story very differently.
Aerith will die one way or another. She must. Whether she is murdered in cold blood or deliberately sacrifices herself doesn't matter to the original story. As long as she dies and summons Holy. The same goes for Cloud's further story and the Black Materia (the reason why Sephiroth needs Cloud so urgently).