The results I got from testing this plugin were the closest I could get to what I had in mind. I was really tired of testing out plugins that required you to have a multi-installation of WordPress (or whatever you call it), when I found a link to this one on the Contact Form 7 page. The results were pretty good overall, but I feel that it still needs more development, although it is definitely on its way to being a 5-star plugin. I will personally keep it deactivated until some flaws are corrected:
First of all, you can't add a language to a page/post unless you change the back-end language first, and I had a hard time figuring it out. I wasn't able to find this step in the installation guide either.
Second of all, the plugin isn't translated. At least the language selection should be. It's ok for the back-end to show the different languages in English, because I don't mind, but I think that the front-end users should see the selection they need in their own language. For instance, if a user needs my web in Spanish, they should see the link as "Español", or at least show some country flags to click on and then show it in the correct language. This is important especially if my web isn't in English.
Third of all, you can't select which language to show on the widget. At least it didn't work for me. Every language ".mo" file that you have uploaded will be the ones that will appear on the widget, even if they don't have a translation available; it will appear as a non-linked word. Yes, delete the ".mo" files that you won't need, that will solve the problem... But if I want my page on Spanish and Portuguese, I don't want to have to delete the English file to hide the English link.
Fourth, and most important of all, there isn't a way to translate the menus. I have seen a solution in the support forum that involved modifying the "Functions.php" file so that it would show one menu or another depending on the language selection made, which also involved having to make two separate menus. I have no problem with that, but I understand that it isn't very user-friendly for most of the administrators.
As I said, keep up the good work. The moment that these flaws are corrected, I will enable the plugin right away!
PS: This plugin works great with the Custom Permalinks plugin! Tested it out myself!