And I won't speak here of players that want to play the game in Russian, Italian or Turkish. They could say you exactly the same thing as me, which will be my conclusion: even if you see this as unkind, I can't see how you could be more wrong about your assumptions of who EU4 players are when not in your own comfort zone.
Former simplified-chinese mod translator here. Localisation x achievement is basically a disaster in EUIV.
1. At least Italian and Turkish are written in Latin alphabet, so I think that dynamic province names and characters' names are less affected in that situations. The problem lies in Russian, Japanese, Korean and Simplified Chinese, which are NOT written in Latin alphabet. To make achievements acquirable, dynamic province names and characters' names are left untranslated so, try to imagine that your game prints something like
"King 约翰 III has succeeded in 巴黎 in France" blabla. This is similar to the situation that I meet, in the sense of functional equality.
2. There has almost been no text left in hard-core files instead of localisation files since CK3 -- dynamic provinces' names and characters are written in localisation filefolder so basically speaking, such situation exists no more in simp-chinese since CK3. I noticed that in French localisation, there seems to be much codes helping with the grammar in scripted-localisation, so the situation might be different.
3. That leads to a new question of the importance of localisation x achievement: once PDX localisation department has offered something that is of a not-that-good quality, things would get difficult. For example, Vicky 3 is known for its low-quality in simp-chinese localisation with many strings left in hard-core files instead of in localisation filefolder. These strings can only be presented in english language in all localization -- if there's
no [achievement acquirable with mod active], playing would be kinda harmful.
As a result of which, [achievements acquirable with mod active] does can cover up for the imperfection of localisation.
Okay, I'll addendum my comment. UI and language mods.
And things can not be just/simply solved in this way, considering that gfx and localisation filefolders have loog been excluded from checksum/vanilla/achievement.
(I noticed that in CK3 and Vicky 3, UI and language mods do affect the checksum. No idea why.)
So yes, I've worked as a madman on everything I could. But I can't say I'm satisfied with the current situation, as there's still far too much issues.
I admire your effort. Seriously speaking it has gone long over the necessary labour. So I admire your devotion too.
Anyway, it's good to meet a colleague here.