I thought since you said PS4, you meant that it would be on the PlayStation 9.
I think a remake would need to have:
-More compilation references/flashbacks
-A more interesting Nibelheim Incident flashback that corresponds to CC
-Better character development, goes along with compilation references
-Sapphire WEAPON as a superboss
-Sephiroth(s) bosses more difficult
-Better translation
-New content (New areas on map, Golden Saucer minigames, Materia, etc)