The workflow itself discussed in the What is Stack Exchange's workflow for handling bugs and feature requests? (thanks @Shadow Wizard).
Question about languages of a post: General idea here is that we want developers understand all information addressed them without somebody's help. It means if you want a feature-request gets implemented probably it's better to write it in English at least. At the same time not all users of an international site want/like/can discuss feature requests in English, so it's worth using the language of a community too (otherwise, probably, it's better to post a feature request directly on MSE).
I updated the post on Meta Stack Overflow in Russian. Now it covers feature-requests as well.