To add to what Gordon wrote:
I wouldn't mind a language pack to that extent, but for a localization
hosted on mozilla, we'd need a current audience.
I'd also suggest to investigate technical means to do the transcription
from the Cyrillic one (we do that for Serbian, for example).
https://gist.github.com/Pike/6525641 might be something you can adapt
via Belarusian-Latin/BGN ?
Axel