All of the best JRPGs I know of prior to the PS3 era had a blend of a grand open world with a great storyline. Secret of Mana, Tales of Symphonia, Vesperia, and Phantasia, all of the FF games prior to X, All the dragon quest games, Chrono Trigger, xenoblade chronicles, late game of FF13 etc... You could probably qualify most pokemon games and earthbound. That's just what I can name off the top of my head. If they are not able to accomplish this now due to a lack of technical power I would have told them they shouldn't even attempt to remake the game and if it turns out to be the case i wont be buying the sequel.
The open world part is what allows JRPGs to continue to be fun outside of the main story and in FF7 80% of it or more takes place once you leave midgar. Otherwise we're going to be left with another "repeat the entire story now on hard mode" or some variation of KH3/KH2 data bosses as end game content; and you might like that but I've been trying to and I just can't. I maxed out all my character levels about an hour and a half after beating the game and almost fully upgraded all my materia; pouring a ton of time into repeating the same bosses/story over again just to upgrade my weapons a bit more or for 1 or 2 optional boss fights to get an accessory that I won't need after the fact simply isn't appealing to me at all.
Are those all really considered to be open world though? I for one remember being fairly gated throughout the first half of Final Fantasy VI. To get out of the beginning desert area you have to complete the Figaro Castle section. Every dungeon is linear, and you have to do specific things to be able to go to specific places. The only point in the entire game that you get full freedom is after Kefka does his midgame victory, and it's all pretty much just a gather-the-party and grind to beat Kefka.
Chrono Trigger has a large world map but it also has a very, very linear story. Yes it has splits and choices and a gazillion alternate endings, but I for one can't remember much actually being optional in that game that wasn't tied to the main story. There weren't really any "side quests".
When most people think "open world" game they think of Skyrim, or Zelda: Breath of the Wild, or Red Dead Redemption. In those games story tends to be treated in and of itself as mostly optional. You might have a short section of linearity to get your bearings, but after that you're allowed to reach most points of the map at your own discretion. And in order to have a good plot, you have to sacrifice open-ness. To have truly open gameplay you have to sacrifice plot.
Breath of the Wild is considered a great game merely from the gameplay. The main complaints center around the story being weak for a Zelda game, since you can tackle anything in any order and it's ALL literally optional, it makes it lose a lot of impact.
Red Dead Redemption 2 is opposite of that. It is considered to have one of the best storylines in recent gaming history, but to do that it has to prevent you from going to certain places too early. And it suffers from the problem that, for those gamers who play primarily for story, once said story is done you lose the drive to keep playing for all the side stuff. The Impact was in the story and now it's gone.
For some players story is higher on there priority list than gameplay itself. It's one of the reasons that I liked KH1 and CoM over KH2. Also, open world games are way less replayable than linear ones in my personal opinion. I've played Zelda: Majora's Mask way more often than I probably ever will Breath of the Wild.
It really is just up to personal taste.
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