I'm not sure if this post is going to be heard by the devs, but here it goes...
I did some research in regards to the legality of using the same art style as Yoshida in the creation of the game, including the models and such. Have to go through reddit and discord to ask people who knew of such laws in Japan in regards to copyright law on whether or not is it alright for you (little orbit) to create a similar art style as Yoshida's for the game.
What I have found out is that you may be able to use the same art style, or at least, an imitation of the art style, since according to copyright laws in Japan, it is allowed for you to create the derivation of the art style even if it's for commercial use. Just don't say that this is Yoshida's art, since he hasn't worked on the art in the first place, so that you'll be in the clear with Square Enix. It's a common art style that is being used on most medieval themed games in Japan, so it isn't far-fetched for you to do the same.
Now the decision is up to you. I just hope that it is possible to delay the game deadline by 4 months (time since you put out the first models, not sure exactly when did the art concept started) or maybe take some effort to remake the models and environments so that you may be able to deliver the kind of style that the backers wanted. Maybe hire or offshore some work to people who have the knowledge of the Medieval Anime (I don't know what that art style used in FFT is called, was it that?) art style for them to work on the concepts and eventually the models for characters and environments. Just don't rush through the process, lest it would lead to a low quality product.
Lile I said, the decision is up to you. I'm just a guy who hasn't backed this project, but I have seen the potential that this game has to offer and I don't want to see it go to waste. Ever since you stepped into the picture after the malicious schemes that Playdek did, everyone saw hope in the fact that this game could finally become the game that everyone was waiting for, the game that could reinnovate the Tactical RPG genre, the one that could make Square Enix rethink of the potential that this genre might hold. By the very act of stepping in to the development of this game, you have inspired both backers and developers. That a dead project that has been forgotten, lost, and was heavily criticized by people for being underdeveloped could have the greatest potential for success in every aspect of its design, and that there is still hope for that potential to be unleashed into the world in a way that could inspire more people that would allow them to dream again, even after a failure.
I could only hope for the best for the finished product, that it would be inspiring and that it would share a similar hero's journey in its road to development.
I do hope that I would be able to inspire the team in this regard.
Good luck and God Bless!