Allow users to select their preferred multiple content languages

Greetings,
I have written about this feature request 1.5 years ago in 5.x, but because everyone was busy porting to 6.x, I was told that this would be a useful new feature and I should raise it again in 6.x. So here I am.

I have created 2 screenshots (see attachments below), which show what I mean.

The basic idea is that users (preferably anonymous users too) will be able to select more than 1 content languages. So they can keep their interface language in English, but also read news in English, Spanish and Russian if they prefer (all in one stream of news), but not ALL content in ALL other enabled languages that they don't speak.

I have seen many websites do this. For best example visit www.reddit.com and click on the language link in top-right corner.

Usage scenarios: Example.com is a community site with many diverse users from around the world. There are 9 enabled languages. Most of these users are multilingual and can read more than 1 language. Some can read content even in 4 or 5 languages. The content is being posted at a very rapid speed by users in all 9 languages, so there is no time to translate of synchronize, and translation/synchronization doesn't make sense in the context of the kind of site that Example.com is. Because most users on the site are multilingual (as many people are these days), they would rather see all content in the languages of their choice pouring into 1 stream or news, rather than having to click through the various languages of the website.
The problem is that there is no way to do this. If you set content settings as "All languages" then ALL content pours into the same stream regardless of whether users can read it or not. This is very bad user-experience and it's very alienating to the users, as it immediately creates the sense that one of the language groups dominates and therefore this site is not for them. For example: Mary can easily read English, French and Spanish, but she cannot read Italian, Russian, Arabic, Greek, German and Portuguese -- therefore she does not need to see content in those languages in her stream of news.

What I propose is that in addition to the current Interface language choices in user account settings, you also include a new form with checkboxes for selecting multiple Content languages. Ideally, this functionality would extend to Anonymous users, in which case a language preference form can open up with Popup module.

This could work with "All content. No language conditions apply" or you could create a new option in Content Selection settings "Only those languages selected by current user".

No more than 100-200 lines of code should be able to do this.

Anyway... just look at my screenshots -- they are pretty self-explanatory.

What do you think?