We have already working association mechanism between Stack Oveflow in Russian and Stack Overlow in English.
Something like this
Text translation: This question has answers on StackOverflow in Russian. [Link to associated question].
My suggestion: I suggest to extend the same mechanism to all Stack Exchange sites.
If very similar (nearly the same) questions were asked on different Stack Exchange sites (that have some topic intersection) we can show link under associated questions
This question has answers on [StackExchange site of associated question]. [Link to associated question]..
This will increase visiting of other Stack Exchange sites and knowledge transfer.