What I did:
1. download English names for everyone from Mod the Sims
2. open it in Sims 4 Studio
3. open "tuning", there are categories that are then divided in different languages. First category is just the names that are generated in CAS and should be use for random townies (but aren't), then categories: Latin, Maroccan, Indian, Japanese and then one for Pets and Skeletons
4. Each category is not only divided in different languages but also to three other categories - female names, male names and surnames
5. Copy the biggest category female names (the first category) and past it in "female" categories in categories for the Latin, Maroccan, Indian and Japanese names
6. Repeat this with male names and surnames
7. Save it - now your NPCs will have different names than just few Japanese ones.
https://i.postimg.cc/zD7LvDtp/screenshot-1542737959.png
https://i.postimg.cc/BZ7qRjwW/screenshot-1542738050.png
https://i.postimg.cc/Z5SKx1M0/screenshot-1542738179.png
https://i.postimg.cc/Bb9dGGDK/screenshot-1542738351.png
https://i.postimg.cc/jdqMn5sj/screenshot-1542738459.png
I play with the English names so I am not certainly sure if you should alter other two tunings (under "tuning") and change something there if you want to use this with your language names. What I noticed is that all original names are preserved and it is just changed in the first part to "ENGLISH" so maybe it will be enough to change your language back (i.e. instead of cz-cs: ENGLISH to cz-cs: CZECH)
https://i.postimg.cc/TwykwHGJ/screenshot-1542737740.png
I am at the club with my sim now and townies are called: Kiley Cary, Dustin Broke, Riley Redd, Lewis Lloyd, Simon Brewer...