Is it possible for an addon to control the i18n files used by other addons?

[Lykeion]

I've recently been working on helping my localization team with the bilingualization of ESO. We have a great plugin that allows ESO to display our local language and English at the same time, which greatly facilitates communication between our local language players and English speakers.

But we are having some problems. Our bilingual mode needs to use its own language code, just as EN for English and FR for French. This poses the problem that even if an addon implements i18n, it will obviously not have a string file corresponding to the language code of our bilingual version. Even if it has our local language version, its language will fall back to English by default in bilingual mode.

My team can customize this for common addons by making a copy of our local language string file and saving it as a bilingual language code version. But that's obviously not a smart way to go. Is it possible to have an addon that maps the language used by other addons to B when it detects a language environment of A?