Same with Light Warriors.
The Japanese version DOES call them Light Warriors (hikari no senshi). The crystal warriors thing is just what the elf prince calls them in that specific bit of dialogue, it's not meant to be a title. Personally I'd go with "warriors of the crystals" in that particular scene.
Imagine if after so many years, after so many re-releases, after Dissidia, after World of FF, after all the other games in the franchise that use the names, Square decided to remake FFVI and change the party members' names to their Japanese counterparts: Tina, Mash, etc. And then after outcry over how unnecessary and alienating it was, Square's defense was "The original version(s) of FFVI are still available to play and we think if people are that attached, they won't be playing this anyway". That would be so unprofessional. Square would NEVER do that. When retranslating a game, you need to think about if the original developers had retranslated it themselves in the modern day. You need to think about what they would and wouldn't do, even with all the capital in the world.
Square does that ALL the time, to the point where extremely little in English Final Fantasy has consistent names at all. And hell, it's not THAT long ago where a rom hacker that would've suggested using names like "Firaga" in a translation hack of an FF game would've been bombarded with all kinds of accusations of unprofessional orientalism and screamed at that neither Square nor any other real translator would've ever considered using such nonsensical word salad in a translation over the sensible "Fire3".
And since you mention FFVI and its names, Square has flipflopped back and forth between calling the purple octopus the accurate "Orthros" or the inaccurate-but-it's-what-I-grew-up-on-so-it's-better "Ultros" ever since the game got released, with neither name having established itself as "what he's going to be officially known as in English from now on". The names of actual main character names may have come to be regarded as sacred, but everything else seems to be pretty free game as far as preserving the inaccuracies people are used to go.
Also, I do have to say, with the disclaimer that it's incredibly unlikely I'll ever use this patch no matter what, that I agree it seems kinda silly to push this as an "accurate representation of what the original FF1 actually was like" if you're going to toss in rewritten bits and bobs from various localizations. You mentioned earlier that you were a bit worried about people accusing you of making things up for stuff like the rat tail description etc, and I can guarantee you that the moment anyone sees Garland threatening to knock them down, they're going to spend the entire rest of their playthrough wondering whether or not this or that bit actually IS what the Japanese version said. This thing isn't going to be played by bilingual players sitting there comparing scripts, it's going to be played by English speakers that were promised a translation that actually accurately translates the original script, and they're going to get suspicious the instant they encounter a line they KNOW isn't accurate.
I mean, it's your patch, obviously, but by presenting this as an actually accurate retranslation that actually represents what the original said, you're kinda building demand for an ACTUALLY accurate retranslation that ACTUALLY represents what the original said here. And I don't think that's what you intended.
(as for the four big boss dudes, I'm pretty certain the Origins translation called them the Four Chaoses)