Yeah there is a way since its been done for the english ones. There is tool for unpacking the sounds, unfortunately this breaks the naming so you have to go through all the sounds and rename them back to the correct name. Then you need specific version of XACT and the original fa project files to pack it back together in the correct format and settings. That alone is kinda annoying. After that there's the patching process which is extra manual work for server admins to push the new voice files. And with the current system I dont think there is a way to include it only for those that would use them. It would have to distribute all languages to everyone. Overall I'd say it's not worth it right now.