Please add the ability to override language of the login page (or browser-based locale detection)

Let me explain the situation first.

We have clients speaking different languages, so ideally they should see the login page in their own language, not the system's default locale. But since we also have a much larger user base poorly understanding English, we're keeping our system locale set to Russian, and that confuses our English-speaking clients.
What we need right now is the ability to over-ride default language for only the login page without touching the system locale, with, say a parameter (login.jsp?lang=en). Is that even possible with the current release of JIRA?

Another possible way would be to automatically detect users' locale based on browser settings.