Native languages and ATC will always be a hot potato and a line has to be drawn somewhere.
However the use of a common language did save my bacon last year down in the Indian Ocean when descending into a island where French is commonly used. I was cleared to the same level as a slower aircraft ahead and we were both instructed to proceed to the hold. Had French has been used, would my next line of defence had been the TCAS?
Hats off to the Russians if they are making moves to introduce English throughout.