Customize FaLang component on a Joomla 2.5 site with K2

We have recently migrated our site from Joomla 1.5 to Joomla 2.5 with K2. It's a news site with over 26.000 articles. The main language is portuguese, but we have around 100 articles translated to english and spanish. We're using the FaLang component to handle the translations. We're having a problem with the component's behavior. When someone opens an article in a language other then portuguese he'll start navigating on that language, with a prefix added to every URL (en or es). It is causing several issues. Our comment system (Intense Debate) handles comments by URL, and we end up with comments spread through all languages. Facebook likes are also affected, as people like an article on different languages and the counter for every language shows a different number ("stealing" likes from the portuguese version). We need someone to customize the component in a way that only the articles that actually have a version other then portuguese receives the language prefix on the URL. So only the articles with translations would show the option to change the language, and when people go to those translated articles and click elsewhere they're brought back to the URL without the language prefix.