Manual Override of Runtime display Language

In K2 5.8 the new feature for Form Translations works by determining the language from the "Accept-Language" value within the HTTP Header, which is a configuration setting of the browser. This works great, however it would be even better if we have a means to override this behaviour and force the Runtime display language using something like a query string parameter or calling a Form Rule.

The requirement here would be that the user can initiate the change of language directly from the form and/or from links allowing the user to choose the language.