Crew languages are based on the airline nationality, since while is completely unrealistic to assume that, just because you can fly anywhere in the world, the crew would speak in different language (and different voices as well), each time you land in a different country, it's not too unrealistic to assume that, not only they would speak in the airline-own language, but also there might be a number of passengers preferring to fly an airline from their own country, and that's also why the percentage of national language words is keep to a minority of a about 20%, compared to 80% of words which are English, in any case.
Now, Wizz Air is a bit on unfortunate example, because the airline is Hungarian, but we don't have Hungarian accents voices, so we choose English/German for Wizz, because it seemed "less wrong" than British or even worse American English. Clearly, adding new languages is always an option, which we did many times in the past, since we have far more voices today than even a year ago.
