You can change it in SimPE, if that's good enough for you. The sim's name is stored in the CTSS in their character file, with the first name on the first line and the last name on the third line, so to copy the name to all languages you would just use the "copy string to all" option. I believe this issue only affects sims created in CAS. Premades also have different names in different languages, although those are generally intentional on EA's part and not random.