The voice changes in FS #9067 are more of a proof of concept at this point. Splashes and menus should be automatically voiced due to the ID2P() macro. Blackjack also includes some explicit voice changes and in theory you could probably play a hand or two without using the screen.
The actual voicing is just roughly done for Blackjack and so it is fairly confusing. I haven't touched any other plugins at this point other than Blackjack, Chopper, and Chessbox. Basically all strings in a plugin will be moved to the lang files unless it makes sense for them to be hardcoded. Blackjack's start page is untranslated because I plan on reworking it with a menu at some point.
