File validator on the FFXIV Boot Launcher

[Singularity]

Yes, it would. But you probably don't want to run a file check on the whole dat every time you launch the game. File validations are typically done by taking a hash value of a given file and then comparing it against the hash on the server's side. The game is over 40GB big however, so validating every file would take time, meaning a sensible implementation of this would just run when the player chooses to do so.

The way game mods currently work is bad anyway, you don't really want to write custom stuff in the game files themself.

You could also have it continuously hashing files in the background, verifying each specific file only when the game actually needs to load it, maybe with some heuristic prediction for what the game will likely need next to reduce impact on loading times. That way it doesn't have to validate the entire thing at once and has minimal impact on gameplay.