Supporting redirects can be simple, depending on your SSG (and it's possible to make extensions to most of them, so this could be something that responds to a posts frontmatter). It could just generare an html file with this

    <meta http-equiv="refresh" …>

sent in the head, and some html/css to make it pretty. It's not ideal, but I assume search engines support it (dunno if there's any additional SEO improvements).