Some interesting things mentioned in the interview:
new mechanic allows the player to use synergy commands and abilities freely at any time by using up a gauge charge in a similar manner to Limit Breaks.
We’ve also added skill trees as a new element of character growth
Many new Materia with new abilities not seen in the first game are available as well, so players will have even more options to customize and build character loadouts to their own taste.
Red XIII doesn’t just have an ATB gauge but also uses his own unique “revenge gauge” mechanic.
[Red XIII] will become an official, playable party member starting from Final Fantasy VII Rebirth.
extended side content based on a summon who did not feature in the original Final Fantasy VII.
[added] a huge number of mini games on a scale that surpasses even the original
The world map is vast and expansive, so not all of the locations on it will be used in the main story alone.
a player’s levels and abilities will not carry over from one game to the next
If you played the original Final Fantasy VII, I’m sure you can guess which scene I’m talking about. You will be able to control Sephiroth in the same scene in this title as you did in the original.
Can only speculate why;