If I didn't know better, I'd say that developing Final Fantasy XV sped up development for the Remake.
Midgar finally looks like a place you can explore and talk to people in (if that's the case, I can only imagine how big some of the in-game dungeon areas will be, like Nibelheim Mountains and Caverns).
The Battle System looks very much like FFXV's (if Duscae is any indication), though I don't know how character switching will work this time around, it should be fun.
Summons and other stuff shouldn't be too hard to implement.
Cutscenes will probably be arranged a little differently, as instead of having "partial control" over Cloud when he gets cornered by the Shinra Guards, they just had him get surrounded and quickly escape on the train in one big cutscene.
I'm pretty sure lots of fans will be in for more surprises and probably do a comparison video between the original game and this once it's fully out there.
The game will also probably be a lot more balanced compared to the original. Manipulate was probably one of the best Materia in the game, as I recall, and using that to train your allies in to using/abusing Limit Breaks was way too much fun, but probably wouldn't work in a game like this.
That said, Limit Breaks might be a bit more action oriented than before. I think that was Climhazzard we saw, but I could be wrong.
) ... but could be better.