I don't think so. The apache man page says:
-f config Execute the commands in the file config on startup. If config does not begin with a /, then it is taken to be a path relative to the ServerRoot. The default is conf/httpd.conf

So even if you started it as httpd -f -, it would only try to open a file called /(serverroot)/-.

You could replace httpd.conf with a named pipe, but you would have to be very carefull: if the process tried to re-read it's config (for instance, if it received a kill -HUP, and you weren't ready for that, apache would hang waiting for input...