1. Your specific file is nro and can't be used because of keys and hashes. Only way is to wait for implementing ease_nro_restriction in atmosphere as it works properly only in dev units.
I was looking at this method earlier and repeated this many times.
NSO in this game is only a forwarder to NRO launcher.
Like I said. I don't really know for sure. You are saying what you know that doesn't work. The instructions do chain from file to file, and there might be a weak link that doesn't require ease_nro_restriction. Just changing the location of two files had a profound impact, but there is a problem we haven't determined the source of. On the note of skepticism, it seems like subtitles trigger voice files, and for dialogue of English lines, there are more lines than there are Japanese. So that might be providing extra complication.
2. Doing kip like that will slow down whole system as it would check every byte and it needs to do it before game will try to set language from string. It would be a nightmare.
Some kips work with key-combos, so I still think that a creative application could be made. Maybe it could operate on a timer, or self-kill after the first instance of a specific byte sequence (instruction)? Also, an NRO can be used to disable/enable the kip, or maybe even toggle what games it operates on. It's cool that you seem to know a lot of things that I don't, but it seems you are already resigned to a specific outcome.
Also, if i'm not mistaken that scene that appears and seems broken, it's at the begining of the game.
Yeah. I tried to be clear about it when I mentioned it. I'll be more specific for you. It is the scene of Zanarkand Ruins that is the setting for both the intro Credits, and when you start a new game. It appears briefly, when the credits start in the beginning, and you don't see it like that at all when you actually start a new game. It looks like it is where the camera is at rest, and isn't supposed to be seen. Maybe, normally it's only resting like that in memory when the screen is black, rolling the credits, before readying the scene. It looks to be a timing mismatch.