>>> ...would like an (optional?) redirector-service on port 80
>>> to simply send a "Location : https://$HTTP_HOST$QUERY_STRING" to

> To me this would be like changing a telnet or ssh port for security
> but having the box accept it anyway.

I'm not qualified to comment on the analogy,
but I know that my ISP does this with webmail.

webmail.bway.net is automatically redirected
to https://webmail.bway.net

I like it.  It saves typing.
I don't know if it's dangerous -or why it would be.