I think Stephen's idea about separating US and UK English deserves discussion, at least.
One reason is that there are many subtle differences that can dramatically alter people's impressions about a translation - examples: some uses of should versus would, or shall versus will, and even rules of punctuation.
Perhaps it is not feasible, since eligibility to participate depends on members' working language pairs. But if it could be worked out, it would reduce the number of contestants in each contest and enable more close scrutiny and more concentrated voting. One could perhaps enter a translation in either one of the two, but could vote in both UK and US. ??????
Other ideas, anyone?