I've already thought about this for the ODS 30AE mod, but you'd need to spend money for those AI services that generate audio speech files, I haven't found viable freeware sources, and you'd also need a lot of patience and free time as a single complete speech pack requires more than 1,400 audio files. Do it for several languages, and you'd need to multiply that amount for each language/accent you intend to have. Those services cost money and the ones I had seen do not allow to automatize the creation of several audio files in one go, so they also cost in terms of time. I'll probably consider it at a later time, but that would mean spending my own money and what little free time I get over something that only few Strike Fighters fans would appreciate all for free.
EDIT: That being said, it surely is the easiest way we currently have to make a more professional speech pack, but not as easy as I'd like.