You can now add a custom vox.
The best way to do this is to create an addon with your files (.mp3 or .wav only)
In a directory with this filepath:
sound/ctts/vox/subtypename/charactername/audio files
the same goes for the constant vox BUT it can only support 1 audio file and it MUST be the same as the charactername in the path or it will not work! And replace the "vox" directory with "constantvox".
Keep in mind in multiplayer the server must also have the files or if its a listen server your friends must have the files as well.