How much is the game held back by technical constraints?

[DPZ2]

I was under the impression that SE used an extremely modified (to the point where it is no longer Crystal Tools) version as the basis for the ARR engine.

The Luminous Engine, as far as I can tell, was used for Final Fantasy XV and ... Forspoken?

No confirmations about Final Fantasy XVI's engine, but it is definitely not the FFXIV engine, nor Luminous. According to the title of an article on cgworld.jp in 2023, 独自エンジンによる、アートとリアルの中間をねらった画づくり〜『FINAL FANTASY XVI』（1） 開発環境・画づくり篇 ... (key words being "proprietary engine" and "development environment).

Autotranslate in Edge provides: In addition, this game is developed with a newly designed in-house engine. Mr. Honda explains, "Considering the man-hours required for support when using a general-purpose game engine or an in-house engine, it was more suitable to develop and manage it ourselves from scratch."

[Source: https://cgworld.jp/article/202309-cgw301-ff16-01.html ]

[Catwho]

Cosmetics are one thing, but sooner or later, with a mobile game, and if it does pick up, you'll start to see the more sinister parts of F2P games show up. Roadblocks added to your progression to make you pay for some currency or some item that relieves it.

On a traditional MMO they can't do that because the playerbase wouldn't accept it, but on a mobile game it would be completely normal. Pay to uncap your tomestones, pay for the daily roulette battle pass... Who knows, they could even invent a new feature just to add gacha mechanics to the game

We already saw it - completing some shiny weapon in the mobile version costs around $250 if you want to pay for all the currency instead of earning it.

[Jeeqbit]

I was under the impression that SE used an extremely modified (to the point where it is no longer Crystal Tools) version as the basis for the ARR engine.

The Luminous Engine, as far as I can tell, was used for Final Fantasy XV and ... Forspoken?

The entire point of getting rid of 1.0 and remaking the game was to not use Crystal Tools. It uses a different engine than Luminous, but it's similar in structure. Some of the people working on FFXIV at the time had worked on Luminous.