I don't think we have any proposals for language-supported tagged unions (have to do them yourself), tuples (write your own macro/struct), or pattern matching (

I don't think we have any proposals for language-supported tagged unions (have to do them yourself), tuples (write your own macro/struct), or pattern matching (lole). You'll have a hard time pushing for those: C will likely never get them in those forms. At least, not for another 10-20 years, since there's no existing C compiler that implements any of those things yet.