Final Fantasy 15 was originally in development at Deus Ex studio

gamesradar.com:

Final Fantasy 15 was originally in development at Guardians of the Galaxy studio Eidos Montreal, it's been confirmed.

Speaking to TrueAchievements in a recent interview, former Eidos Montreal art director Jonathan Jacque-Belletête confirmed the long-standing rumor. "We tried to do Final Fantasy XV. Then they decided to bring it back to Japan — which I think was a big mistake, but it's still the truth. Ours was really, really cool," said Jacque-Belletête.

Unfortunately, the developer didn't elaborate further on the project. As TrueAchievements notes however, this comment finally confirms a rumor originating from a SuperBunnyHop video in 2018, seen just below, where the YouTuber claims that Final Fantasy 15 was once in development at Eidos Montreal, according to several anonymous sources.

According to the original SuperBunnyHop video, Eidos Montreal had "some basic art, some basic game design, in a super-secret office." The 2018 video also claimed that the project was a "space opera RPG" with a love triangle, and Jacque-Belletête's new comments certainly lead a lot of credibility to the full video.

Unfortunately, it just wasn't to be. Square Enix would end up taking Final Fantasy 15 back to Japan, where it would be rebooted and retooled under Hajime Tabata once Kingdom Hearts director Tetsuya Nomura departed the project. Final Fantasy 15 released in 2016 after over a decade of development, and just recently surpassed 10 million copies sold, which is actually the goal Tabata and his team originally set for the RPG.

Here's how Final Fantasy 15 influenced Forspoken, Square Enix's upcoming big-budget action-RPG.