Hi Maverfic,
I think that would do nothing unless the controller ensures every single direction, clearance etc. given to any pilot (on one or the other freq) is heard on both frequencies on its respective language. That added to continuous frequency switching would greatly increase workload and likelyhood of mistake.
If what stated above is not carried out, how can a pilot on freq. #1 be aware of the instructions issued on freq. #2 to another?