I think it's a good idea, but if the indicator of translations sits among other menus, it may be slightly confusing. (In this case, the meaning of flags is slightly different from the one of other menus, isn't it? They are not submenus of Languages menu.)
Moving flags to, say, top-right corner of the main page looks sensible because the flag switches "individual" pages, but I'm not sure if this is too complicated to code or not. (Or moving flags to top or bottom of the side bar and remove descriptions?) > I'm not sure how this different flag icon should like like though... For example, the same flags with faded color? Koji