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You're confusing different FSR implementations.
FSR 2.0 is a temporal upscaler that also uses movement information,
FSR 1.0 is a pure spacial upscaler.
Also your initial statement about not being allowed to modify game files is demonstrably false. There's a comment by mofu telling someone to modify the translation.
There's also no legal basis for it.
You probably meant that people are not allowed to distribute modified game files, which a separate issue.
The waifu2x upscale is done btw.
I will not upload it, don't worry.
I haven't bothered to look into repacking, just wanted to demonstrate that it can be done fairly easily.
If someone here wants to see the quality change they can take a screenshot and run that through the waifu2x website; for getting an idea of the quality of the upscale that's good enough.