Imo the non-English voices speaking English aren't that useful as accented voices, because, at least for the Latin-alphabet ones, they're dominated by spelling-

Imo the non-English voices speaking English aren't that useful as accented voices, because, at least for the Latin-alphabet ones, they're dominated by spelling-to-phonology mapping errors, like misreading diphthongs. It's an okay representation of someone who really speaks no English trying to sound out written English as if it were German, but it's not very similar to what a German accent in English sounds like, since a typical German accent isn't dominated by misreadings. If it were open source you could probably get better results by hacking it up to parse in the "right" language and then only realizing the phonology in the "wrong" language, instead of both parsing and speaking in the "wrong" language.