if I am not mistaken you can use the wild cards like Juraj mentioned above, but the problem is that you query string will be transferred to the new URL i.e.: \old_homepage.aspx?lang=1 will go \newhomepage?lang=1, but don't need this query string for your new URL :(
So I would say your initial idea was correct: it is either IIS rewrite rule or custom web part.