That looks fantastic! I tried it in a hidden thread in one of my games. Seems to work just fine. I sense a heavy German influence in the sample translation set...
[rlang=language;translator_set]what your character says[/rlang]
At the moment we only have one translation set, anyone that wants another needs to provide me 2kb of nonsense text.
In other words, for now use
[rlang=language]what your character says[/rlang]
People that wanted this should now test it, let me know how it goes.